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func.sgml has grown over the years to the point where it is very difficult to manage. This commit splits out each sect1 piece into its own file, which is then included in the main file, so that the built documentation should be identical to the pre-split documentation. All these new files are placed in a new "func" subdirectory, and the previous func.sgml is removed. Done using scripts developed by: Author: jian he <jian.universality@gmail.com> Discussion: https://postgr.es/m/CACJufxFgAh1--EMwOjMuANe=VTmjkNaZjH+AzSe04-8ZCGiESA@mail.gmail.com
1419 lines
53 KiB
Plaintext
1419 lines
53 KiB
Plaintext
<sect1 id="functions-aggregate">
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<title>Aggregate Functions</title>
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<indexterm zone="functions-aggregate">
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<primary>aggregate function</primary>
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<secondary>built-in</secondary>
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</indexterm>
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<para>
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<firstterm>Aggregate functions</firstterm> compute a single result
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from a set of input values. The built-in general-purpose aggregate
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functions are listed in <xref linkend="functions-aggregate-table"/>
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while statistical aggregates are in <xref
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linkend="functions-aggregate-statistics-table"/>.
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The built-in within-group ordered-set aggregate functions
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are listed in <xref linkend="functions-orderedset-table"/>
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while the built-in within-group hypothetical-set ones are in <xref
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linkend="functions-hypothetical-table"/>. Grouping operations,
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which are closely related to aggregate functions, are listed in
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<xref linkend="functions-grouping-table"/>.
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The special syntax considerations for aggregate
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functions are explained in <xref linkend="syntax-aggregates"/>.
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Consult <xref linkend="tutorial-agg"/> for additional introductory
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information.
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</para>
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<para>
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Aggregate functions that support <firstterm>Partial Mode</firstterm>
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are eligible to participate in various optimizations, such as parallel
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aggregation.
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</para>
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<para>
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While all aggregates below accept an optional
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<literal>ORDER BY</literal> clause (as outlined in <xref
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linkend="syntax-aggregates"/>), the clause has only been added to
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aggregates whose output is affected by ordering.
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</para>
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<table id="functions-aggregate-table">
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<title>General-Purpose Aggregate Functions</title>
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<tgroup cols="2">
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<colspec colname="col1" colwidth="10*"/>
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<colspec colname="col2" colwidth="1*"/>
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<thead>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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Function
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</para>
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<para>
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Description
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</para></entry>
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<entry>Partial Mode</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<indexterm>
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<primary>any_value</primary>
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</indexterm>
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<function>any_value</function> ( <type>anyelement</type> )
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<returnvalue><replaceable>same as input type</replaceable></returnvalue>
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</para>
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<para>
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Returns an arbitrary value from the non-null input values.
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</para></entry>
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<entry>Yes</entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<indexterm>
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<primary>array_agg</primary>
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</indexterm>
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<function>array_agg</function> ( <type>anynonarray</type> <literal>ORDER BY</literal> <literal>input_sort_columns</literal> )
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<returnvalue>anyarray</returnvalue>
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</para>
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<para>
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Collects all the input values, including nulls, into an array.
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</para></entry>
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<entry>Yes</entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<function>array_agg</function> ( <type>anyarray</type> <literal>ORDER BY</literal> <literal>input_sort_columns</literal> )
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<returnvalue>anyarray</returnvalue>
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</para>
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<para>
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Concatenates all the input arrays into an array of one higher
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dimension. (The inputs must all have the same dimensionality, and
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cannot be empty or null.)
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</para></entry>
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<entry>Yes</entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<indexterm>
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<primary>average</primary>
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</indexterm>
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<indexterm>
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<primary>avg</primary>
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</indexterm>
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<function>avg</function> ( <type>smallint</type> )
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<returnvalue>numeric</returnvalue>
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</para>
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<para role="func_signature">
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<function>avg</function> ( <type>integer</type> )
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<returnvalue>numeric</returnvalue>
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</para>
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<para role="func_signature">
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<function>avg</function> ( <type>bigint</type> )
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<returnvalue>numeric</returnvalue>
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</para>
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<para role="func_signature">
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<function>avg</function> ( <type>numeric</type> )
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<returnvalue>numeric</returnvalue>
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</para>
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<para role="func_signature">
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<function>avg</function> ( <type>real</type> )
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<returnvalue>double precision</returnvalue>
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</para>
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<para role="func_signature">
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<function>avg</function> ( <type>double precision</type> )
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<returnvalue>double precision</returnvalue>
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</para>
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<para role="func_signature">
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<function>avg</function> ( <type>interval</type> )
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<returnvalue>interval</returnvalue>
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</para>
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<para>
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Computes the average (arithmetic mean) of all the non-null input
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values.
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</para></entry>
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<entry>Yes</entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<indexterm>
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<primary>bit_and</primary>
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</indexterm>
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<function>bit_and</function> ( <type>smallint</type> )
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<returnvalue>smallint</returnvalue>
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</para>
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<para role="func_signature">
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<function>bit_and</function> ( <type>integer</type> )
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<returnvalue>integer</returnvalue>
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</para>
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<para role="func_signature">
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<function>bit_and</function> ( <type>bigint</type> )
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<returnvalue>bigint</returnvalue>
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</para>
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<para role="func_signature">
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<function>bit_and</function> ( <type>bit</type> )
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<returnvalue>bit</returnvalue>
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</para>
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<para>
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Computes the bitwise AND of all non-null input values.
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</para></entry>
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<entry>Yes</entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<indexterm>
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<primary>bit_or</primary>
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</indexterm>
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<function>bit_or</function> ( <type>smallint</type> )
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<returnvalue>smallint</returnvalue>
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</para>
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<para role="func_signature">
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<function>bit_or</function> ( <type>integer</type> )
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<returnvalue>integer</returnvalue>
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</para>
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<para role="func_signature">
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<function>bit_or</function> ( <type>bigint</type> )
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<returnvalue>bigint</returnvalue>
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</para>
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<para role="func_signature">
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<function>bit_or</function> ( <type>bit</type> )
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<returnvalue>bit</returnvalue>
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</para>
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<para>
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Computes the bitwise OR of all non-null input values.
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</para></entry>
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<entry>Yes</entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<indexterm>
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<primary>bit_xor</primary>
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</indexterm>
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<function>bit_xor</function> ( <type>smallint</type> )
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<returnvalue>smallint</returnvalue>
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</para>
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<para role="func_signature">
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<function>bit_xor</function> ( <type>integer</type> )
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<returnvalue>integer</returnvalue>
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</para>
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<para role="func_signature">
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<function>bit_xor</function> ( <type>bigint</type> )
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<returnvalue>bigint</returnvalue>
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</para>
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<para role="func_signature">
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<function>bit_xor</function> ( <type>bit</type> )
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<returnvalue>bit</returnvalue>
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</para>
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<para>
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Computes the bitwise exclusive OR of all non-null input values.
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Can be useful as a checksum for an unordered set of values.
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</para></entry>
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<entry>Yes</entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<indexterm>
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<primary>bool_and</primary>
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</indexterm>
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<function>bool_and</function> ( <type>boolean</type> )
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<returnvalue>boolean</returnvalue>
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</para>
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<para>
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Returns true if all non-null input values are true, otherwise false.
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</para></entry>
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<entry>Yes</entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<indexterm>
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<primary>bool_or</primary>
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</indexterm>
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<function>bool_or</function> ( <type>boolean</type> )
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<returnvalue>boolean</returnvalue>
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</para>
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<para>
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Returns true if any non-null input value is true, otherwise false.
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</para></entry>
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<entry>Yes</entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<indexterm>
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<primary>count</primary>
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</indexterm>
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<function>count</function> ( <literal>*</literal> )
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<returnvalue>bigint</returnvalue>
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</para>
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<para>
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Computes the number of input rows.
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</para></entry>
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<entry>Yes</entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<function>count</function> ( <type>"any"</type> )
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<returnvalue>bigint</returnvalue>
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</para>
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<para>
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Computes the number of input rows in which the input value is not
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null.
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</para></entry>
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<entry>Yes</entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<indexterm>
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<primary>every</primary>
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</indexterm>
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<function>every</function> ( <type>boolean</type> )
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<returnvalue>boolean</returnvalue>
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</para>
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<para>
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This is the SQL standard's equivalent to <function>bool_and</function>.
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</para></entry>
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<entry>Yes</entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<indexterm>
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<primary>json_agg</primary>
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</indexterm>
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<function>json_agg</function> ( <type>anyelement</type> <literal>ORDER BY</literal> <literal>input_sort_columns</literal> )
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<returnvalue>json</returnvalue>
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</para>
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<para role="func_signature">
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<indexterm>
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<primary>jsonb_agg</primary>
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</indexterm>
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<function>jsonb_agg</function> ( <type>anyelement</type> <literal>ORDER BY</literal> <literal>input_sort_columns</literal> )
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<returnvalue>jsonb</returnvalue>
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</para>
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<para>
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Collects all the input values, including nulls, into a JSON array.
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Values are converted to JSON as per <function>to_json</function>
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or <function>to_jsonb</function>.
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</para></entry>
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<entry>No</entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<indexterm>
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<primary>json_agg_strict</primary>
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</indexterm>
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<function>json_agg_strict</function> ( <type>anyelement</type> )
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<returnvalue>json</returnvalue>
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</para>
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<para role="func_signature">
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<indexterm>
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<primary>jsonb_agg_strict</primary>
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</indexterm>
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<function>jsonb_agg_strict</function> ( <type>anyelement</type> )
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<returnvalue>jsonb</returnvalue>
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</para>
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<para>
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Collects all the input values, skipping nulls, into a JSON array.
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Values are converted to JSON as per <function>to_json</function>
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or <function>to_jsonb</function>.
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</para></entry>
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<entry>No</entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<indexterm><primary>json_arrayagg</primary></indexterm>
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<function>json_arrayagg</function> (
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<optional> <replaceable>value_expression</replaceable> </optional>
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<optional> <literal>ORDER BY</literal> <replaceable>sort_expression</replaceable> </optional>
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<optional> { <literal>NULL</literal> | <literal>ABSENT</literal> } <literal>ON NULL</literal> </optional>
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<optional> <literal>RETURNING</literal> <replaceable>data_type</replaceable> <optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional> </optional> </optional>)
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</para>
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<para>
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Behaves in the same way as <function>json_array</function>
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but as an aggregate function so it only takes one
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<replaceable>value_expression</replaceable> parameter.
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If <literal>ABSENT ON NULL</literal> is specified, any NULL
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values are omitted.
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If <literal>ORDER BY</literal> is specified, the elements will
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appear in the array in that order rather than in the input order.
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</para>
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<para>
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<literal>SELECT json_arrayagg(v) FROM (VALUES(2),(1)) t(v)</literal>
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<returnvalue>[2, 1]</returnvalue>
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</para></entry>
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<entry>No</entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<indexterm><primary>json_objectagg</primary></indexterm>
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<function>json_objectagg</function> (
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<optional> { <replaceable>key_expression</replaceable> { <literal>VALUE</literal> | ':' } <replaceable>value_expression</replaceable> } </optional>
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<optional> { <literal>NULL</literal> | <literal>ABSENT</literal> } <literal>ON NULL</literal> </optional>
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<optional> { <literal>WITH</literal> | <literal>WITHOUT</literal> } <literal>UNIQUE</literal> <optional> <literal>KEYS</literal> </optional> </optional>
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<optional> <literal>RETURNING</literal> <replaceable>data_type</replaceable> <optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional> </optional> </optional>)
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</para>
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<para>
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Behaves like <function>json_object</function><!-- xref -->, but as an
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aggregate function, so it only takes one
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<replaceable>key_expression</replaceable> and one
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<replaceable>value_expression</replaceable> parameter.
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</para>
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<para>
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<literal>SELECT json_objectagg(k:v) FROM (VALUES ('a'::text,current_date),('b',current_date + 1)) AS t(k,v)</literal>
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<returnvalue>{ "a" : "2022-05-10", "b" : "2022-05-11" }</returnvalue>
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</para></entry>
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<entry>No</entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<indexterm>
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<primary>json_object_agg</primary>
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</indexterm>
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<function>json_object_agg</function> ( <parameter>key</parameter>
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<type>"any"</type>, <parameter>value</parameter>
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<type>"any"</type>
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<literal>ORDER BY</literal> <literal>input_sort_columns</literal> )
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<returnvalue>json</returnvalue>
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</para>
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<para role="func_signature">
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<indexterm>
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<primary>jsonb_object_agg</primary>
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</indexterm>
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<function>jsonb_object_agg</function> ( <parameter>key</parameter>
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<type>"any"</type>, <parameter>value</parameter>
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<type>"any"</type>
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<literal>ORDER BY</literal> <literal>input_sort_columns</literal> )
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<returnvalue>jsonb</returnvalue>
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</para>
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<para>
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Collects all the key/value pairs into a JSON object. Key arguments
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are coerced to text; value arguments are converted as per
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<function>to_json</function> or <function>to_jsonb</function>.
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Values can be null, but keys cannot.
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</para></entry>
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<entry>No</entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<indexterm>
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<primary>json_object_agg_strict</primary>
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</indexterm>
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<function>json_object_agg_strict</function> (
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<parameter>key</parameter> <type>"any"</type>,
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<parameter>value</parameter> <type>"any"</type> )
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<returnvalue>json</returnvalue>
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</para>
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<para role="func_signature">
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<indexterm>
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<primary>jsonb_object_agg_strict</primary>
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</indexterm>
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<function>jsonb_object_agg_strict</function> (
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<parameter>key</parameter> <type>"any"</type>,
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<parameter>value</parameter> <type>"any"</type> )
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<returnvalue>jsonb</returnvalue>
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</para>
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<para>
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Collects all the key/value pairs into a JSON object. Key arguments
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|
are coerced to text; value arguments are converted as per
|
|
<function>to_json</function> or <function>to_jsonb</function>.
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|
The <parameter>key</parameter> can not be null. If the
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<parameter>value</parameter> is null then the entry is skipped,
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</para></entry>
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<entry>No</entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
|
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<indexterm>
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|
<primary>json_object_agg_unique</primary>
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|
</indexterm>
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|
<function>json_object_agg_unique</function> (
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<parameter>key</parameter> <type>"any"</type>,
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|
<parameter>value</parameter> <type>"any"</type> )
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|
<returnvalue>json</returnvalue>
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</para>
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<para role="func_signature">
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<indexterm>
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<primary>jsonb_object_agg_unique</primary>
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|
</indexterm>
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|
<function>jsonb_object_agg_unique</function> (
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<parameter>key</parameter> <type>"any"</type>,
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|
<parameter>value</parameter> <type>"any"</type> )
|
|
<returnvalue>jsonb</returnvalue>
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|
</para>
|
|
<para>
|
|
Collects all the key/value pairs into a JSON object. Key arguments
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|
are coerced to text; value arguments are converted as per
|
|
<function>to_json</function> or <function>to_jsonb</function>.
|
|
Values can be null, but keys cannot.
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|
If there is a duplicate key an error is thrown.
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|
</para></entry>
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<entry>No</entry>
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</row>
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|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>json_object_agg_unique_strict</primary>
|
|
</indexterm>
|
|
<function>json_object_agg_unique_strict</function> (
|
|
<parameter>key</parameter> <type>"any"</type>,
|
|
<parameter>value</parameter> <type>"any"</type> )
|
|
<returnvalue>json</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<indexterm>
|
|
<primary>jsonb_object_agg_unique_strict</primary>
|
|
</indexterm>
|
|
<function>jsonb_object_agg_unique_strict</function> (
|
|
<parameter>key</parameter> <type>"any"</type>,
|
|
<parameter>value</parameter> <type>"any"</type> )
|
|
<returnvalue>jsonb</returnvalue>
|
|
</para>
|
|
<para>
|
|
Collects all the key/value pairs into a JSON object. Key arguments
|
|
are coerced to text; value arguments are converted as per
|
|
<function>to_json</function> or <function>to_jsonb</function>.
|
|
The <parameter>key</parameter> can not be null. If the
|
|
<parameter>value</parameter> is null then the entry is skipped.
|
|
If there is a duplicate key an error is thrown.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>max</primary>
|
|
</indexterm>
|
|
<function>max</function> ( <replaceable>see text</replaceable> )
|
|
<returnvalue><replaceable>same as input type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the maximum of the non-null input
|
|
values. Available for any numeric, string, date/time, or enum type,
|
|
as well as <type>bytea</type>, <type>inet</type>, <type>interval</type>,
|
|
<type>money</type>, <type>oid</type>, <type>pg_lsn</type>,
|
|
<type>tid</type>, <type>xid8</type>,
|
|
and also arrays and composite types containing sortable data types.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>min</primary>
|
|
</indexterm>
|
|
<function>min</function> ( <replaceable>see text</replaceable> )
|
|
<returnvalue><replaceable>same as input type</replaceable></returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the minimum of the non-null input
|
|
values. Available for any numeric, string, date/time, or enum type,
|
|
as well as <type>bytea</type>, <type>inet</type>, <type>interval</type>,
|
|
<type>money</type>, <type>oid</type>, <type>pg_lsn</type>,
|
|
<type>tid</type>, <type>xid8</type>,
|
|
and also arrays and composite types containing sortable data types.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>range_agg</primary>
|
|
</indexterm>
|
|
<function>range_agg</function> ( <parameter>value</parameter>
|
|
<type>anyrange</type> )
|
|
<returnvalue>anymultirange</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>range_agg</function> ( <parameter>value</parameter>
|
|
<type>anymultirange</type> )
|
|
<returnvalue>anymultirange</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the union of the non-null input values.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>range_intersect_agg</primary>
|
|
</indexterm>
|
|
<function>range_intersect_agg</function> ( <parameter>value</parameter>
|
|
<type>anyrange</type> )
|
|
<returnvalue>anyrange</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>range_intersect_agg</function> ( <parameter>value</parameter>
|
|
<type>anymultirange</type> )
|
|
<returnvalue>anymultirange</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the intersection of the non-null input values.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>string_agg</primary>
|
|
</indexterm>
|
|
<function>string_agg</function> ( <parameter>value</parameter>
|
|
<type>text</type>, <parameter>delimiter</parameter> <type>text</type> )
|
|
<returnvalue>text</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>string_agg</function> ( <parameter>value</parameter>
|
|
<type>bytea</type>, <parameter>delimiter</parameter> <type>bytea</type>
|
|
<literal>ORDER BY</literal> <literal>input_sort_columns</literal> )
|
|
<returnvalue>bytea</returnvalue>
|
|
</para>
|
|
<para>
|
|
Concatenates the non-null input values into a string. Each value
|
|
after the first is preceded by the
|
|
corresponding <parameter>delimiter</parameter> (if it's not null).
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>sum</primary>
|
|
</indexterm>
|
|
<function>sum</function> ( <type>smallint</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>sum</function> ( <type>integer</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>sum</function> ( <type>bigint</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>sum</function> ( <type>numeric</type> )
|
|
<returnvalue>numeric</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>sum</function> ( <type>real</type> )
|
|
<returnvalue>real</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>sum</function> ( <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>sum</function> ( <type>interval</type> )
|
|
<returnvalue>interval</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>sum</function> ( <type>money</type> )
|
|
<returnvalue>money</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the sum of the non-null input values.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>xmlagg</primary>
|
|
</indexterm>
|
|
<function>xmlagg</function> ( <type>xml</type> <literal>ORDER BY</literal> <literal>input_sort_columns</literal> )
|
|
<returnvalue>xml</returnvalue>
|
|
</para>
|
|
<para>
|
|
Concatenates the non-null XML input values (see
|
|
<xref linkend="functions-xml-xmlagg"/>).
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
It should be noted that except for <function>count</function>,
|
|
these functions return a null value when no rows are selected. In
|
|
particular, <function>sum</function> of no rows returns null, not
|
|
zero as one might expect, and <function>array_agg</function>
|
|
returns null rather than an empty array when there are no input
|
|
rows. The <function>coalesce</function> function can be used to
|
|
substitute zero or an empty array for null when necessary.
|
|
</para>
|
|
|
|
<para>
|
|
The aggregate functions <function>array_agg</function>,
|
|
<function>json_agg</function>, <function>jsonb_agg</function>,
|
|
<function>json_agg_strict</function>, <function>jsonb_agg_strict</function>,
|
|
<function>json_object_agg</function>, <function>jsonb_object_agg</function>,
|
|
<function>json_object_agg_strict</function>, <function>jsonb_object_agg_strict</function>,
|
|
<function>json_object_agg_unique</function>, <function>jsonb_object_agg_unique</function>,
|
|
<function>json_object_agg_unique_strict</function>,
|
|
<function>jsonb_object_agg_unique_strict</function>,
|
|
<function>string_agg</function>,
|
|
and <function>xmlagg</function>, as well as similar user-defined
|
|
aggregate functions, produce meaningfully different result values
|
|
depending on the order of the input values. This ordering is
|
|
unspecified by default, but can be controlled by writing an
|
|
<literal>ORDER BY</literal> clause within the aggregate call, as shown in
|
|
<xref linkend="syntax-aggregates"/>.
|
|
Alternatively, supplying the input values from a sorted subquery
|
|
will usually work. For example:
|
|
|
|
<screen><![CDATA[
|
|
SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
|
|
]]></screen>
|
|
|
|
Beware that this approach can fail if the outer query level contains
|
|
additional processing, such as a join, because that might cause the
|
|
subquery's output to be reordered before the aggregate is computed.
|
|
</para>
|
|
|
|
<note>
|
|
<indexterm>
|
|
<primary>ANY</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>SOME</primary>
|
|
</indexterm>
|
|
<para>
|
|
The boolean aggregates <function>bool_and</function> and
|
|
<function>bool_or</function> correspond to the standard SQL aggregates
|
|
<function>every</function> and <function>any</function> or
|
|
<function>some</function>.
|
|
<productname>PostgreSQL</productname>
|
|
supports <function>every</function>, but not <function>any</function>
|
|
or <function>some</function>, because there is an ambiguity built into
|
|
the standard syntax:
|
|
<programlisting>
|
|
SELECT b1 = ANY((SELECT b2 FROM t2 ...)) FROM t1 ...;
|
|
</programlisting>
|
|
Here <function>ANY</function> can be considered either as introducing
|
|
a subquery, or as being an aggregate function, if the subquery
|
|
returns one row with a Boolean value.
|
|
Thus the standard name cannot be given to these aggregates.
|
|
</para>
|
|
</note>
|
|
|
|
<note>
|
|
<para>
|
|
Users accustomed to working with other SQL database management
|
|
systems might be disappointed by the performance of the
|
|
<function>count</function> aggregate when it is applied to the
|
|
entire table. A query like:
|
|
<programlisting>
|
|
SELECT count(*) FROM sometable;
|
|
</programlisting>
|
|
will require effort proportional to the size of the table:
|
|
<productname>PostgreSQL</productname> will need to scan either the
|
|
entire table or the entirety of an index that includes all rows in
|
|
the table.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
<xref linkend="functions-aggregate-statistics-table"/> shows
|
|
aggregate functions typically used in statistical analysis.
|
|
(These are separated out merely to avoid cluttering the listing
|
|
of more-commonly-used aggregates.) Functions shown as
|
|
accepting <replaceable>numeric_type</replaceable> are available for all
|
|
the types <type>smallint</type>, <type>integer</type>,
|
|
<type>bigint</type>, <type>numeric</type>, <type>real</type>,
|
|
and <type>double precision</type>.
|
|
Where the description mentions
|
|
<parameter>N</parameter>, it means the
|
|
number of input rows for which all the input expressions are non-null.
|
|
In all cases, null is returned if the computation is meaningless,
|
|
for example when <parameter>N</parameter> is zero.
|
|
</para>
|
|
|
|
<indexterm>
|
|
<primary>statistics</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>linear regression</primary>
|
|
</indexterm>
|
|
|
|
<table id="functions-aggregate-statistics-table">
|
|
<title>Aggregate Functions for Statistics</title>
|
|
<tgroup cols="2">
|
|
<colspec colname="col1" colwidth="10*"/>
|
|
<colspec colname="col2" colwidth="1*"/>
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
<entry>Partial Mode</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>correlation</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>corr</primary>
|
|
</indexterm>
|
|
<function>corr</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the correlation coefficient.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>covariance</primary>
|
|
<secondary>population</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>covar_pop</primary>
|
|
</indexterm>
|
|
<function>covar_pop</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the population covariance.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>covariance</primary>
|
|
<secondary>sample</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>covar_samp</primary>
|
|
</indexterm>
|
|
<function>covar_samp</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the sample covariance.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regr_avgx</primary>
|
|
</indexterm>
|
|
<function>regr_avgx</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the average of the independent variable,
|
|
<literal>sum(<parameter>X</parameter>)/<parameter>N</parameter></literal>.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regr_avgy</primary>
|
|
</indexterm>
|
|
<function>regr_avgy</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the average of the dependent variable,
|
|
<literal>sum(<parameter>Y</parameter>)/<parameter>N</parameter></literal>.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regr_count</primary>
|
|
</indexterm>
|
|
<function>regr_count</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the number of rows in which both inputs are non-null.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regression intercept</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>regr_intercept</primary>
|
|
</indexterm>
|
|
<function>regr_intercept</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the y-intercept of the least-squares-fit linear equation
|
|
determined by the
|
|
(<parameter>X</parameter>, <parameter>Y</parameter>) pairs.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regr_r2</primary>
|
|
</indexterm>
|
|
<function>regr_r2</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the square of the correlation coefficient.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regression slope</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>regr_slope</primary>
|
|
</indexterm>
|
|
<function>regr_slope</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the slope of the least-squares-fit linear equation determined
|
|
by the (<parameter>X</parameter>, <parameter>Y</parameter>)
|
|
pairs.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regr_sxx</primary>
|
|
</indexterm>
|
|
<function>regr_sxx</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the <quote>sum of squares</quote> of the independent
|
|
variable,
|
|
<literal>sum(<parameter>X</parameter>^2) - sum(<parameter>X</parameter>)^2/<parameter>N</parameter></literal>.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regr_sxy</primary>
|
|
</indexterm>
|
|
<function>regr_sxy</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the <quote>sum of products</quote> of independent times
|
|
dependent variables,
|
|
<literal>sum(<parameter>X</parameter>*<parameter>Y</parameter>) - sum(<parameter>X</parameter>) * sum(<parameter>Y</parameter>)/<parameter>N</parameter></literal>.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>regr_syy</primary>
|
|
</indexterm>
|
|
<function>regr_syy</function> ( <parameter>Y</parameter> <type>double precision</type>, <parameter>X</parameter> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the <quote>sum of squares</quote> of the dependent
|
|
variable,
|
|
<literal>sum(<parameter>Y</parameter>^2) - sum(<parameter>Y</parameter>)^2/<parameter>N</parameter></literal>.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>standard deviation</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>stddev</primary>
|
|
</indexterm>
|
|
<function>stddev</function> ( <replaceable>numeric_type</replaceable> )
|
|
<returnvalue></returnvalue> <type>double precision</type>
|
|
for <type>real</type> or <type>double precision</type>,
|
|
otherwise <type>numeric</type>
|
|
</para>
|
|
<para>
|
|
This is a historical alias for <function>stddev_samp</function>.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>standard deviation</primary>
|
|
<secondary>population</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>stddev_pop</primary>
|
|
</indexterm>
|
|
<function>stddev_pop</function> ( <replaceable>numeric_type</replaceable> )
|
|
<returnvalue></returnvalue> <type>double precision</type>
|
|
for <type>real</type> or <type>double precision</type>,
|
|
otherwise <type>numeric</type>
|
|
</para>
|
|
<para>
|
|
Computes the population standard deviation of the input values.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>standard deviation</primary>
|
|
<secondary>sample</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>stddev_samp</primary>
|
|
</indexterm>
|
|
<function>stddev_samp</function> ( <replaceable>numeric_type</replaceable> )
|
|
<returnvalue></returnvalue> <type>double precision</type>
|
|
for <type>real</type> or <type>double precision</type>,
|
|
otherwise <type>numeric</type>
|
|
</para>
|
|
<para>
|
|
Computes the sample standard deviation of the input values.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>variance</primary>
|
|
</indexterm>
|
|
<function>variance</function> ( <replaceable>numeric_type</replaceable> )
|
|
<returnvalue></returnvalue> <type>double precision</type>
|
|
for <type>real</type> or <type>double precision</type>,
|
|
otherwise <type>numeric</type>
|
|
</para>
|
|
<para>
|
|
This is a historical alias for <function>var_samp</function>.
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>variance</primary>
|
|
<secondary>population</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>var_pop</primary>
|
|
</indexterm>
|
|
<function>var_pop</function> ( <replaceable>numeric_type</replaceable> )
|
|
<returnvalue></returnvalue> <type>double precision</type>
|
|
for <type>real</type> or <type>double precision</type>,
|
|
otherwise <type>numeric</type>
|
|
</para>
|
|
<para>
|
|
Computes the population variance of the input values (square of the
|
|
population standard deviation).
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>variance</primary>
|
|
<secondary>sample</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>var_samp</primary>
|
|
</indexterm>
|
|
<function>var_samp</function> ( <replaceable>numeric_type</replaceable> )
|
|
<returnvalue></returnvalue> <type>double precision</type>
|
|
for <type>real</type> or <type>double precision</type>,
|
|
otherwise <type>numeric</type>
|
|
</para>
|
|
<para>
|
|
Computes the sample variance of the input values (square of the sample
|
|
standard deviation).
|
|
</para></entry>
|
|
<entry>Yes</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<xref linkend="functions-orderedset-table"/> shows some
|
|
aggregate functions that use the <firstterm>ordered-set aggregate</firstterm>
|
|
syntax. These functions are sometimes referred to as <quote>inverse
|
|
distribution</quote> functions. Their aggregated input is introduced by
|
|
<literal>ORDER BY</literal>, and they may also take a <firstterm>direct
|
|
argument</firstterm> that is not aggregated, but is computed only once.
|
|
All these functions ignore null values in their aggregated input.
|
|
For those that take a <parameter>fraction</parameter> parameter, the
|
|
fraction value must be between 0 and 1; an error is thrown if not.
|
|
However, a null <parameter>fraction</parameter> value simply produces a
|
|
null result.
|
|
</para>
|
|
|
|
<indexterm>
|
|
<primary>ordered-set aggregate</primary>
|
|
<secondary>built-in</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>inverse distribution</primary>
|
|
</indexterm>
|
|
|
|
<table id="functions-orderedset-table">
|
|
<title>Ordered-Set Aggregate Functions</title>
|
|
<tgroup cols="2">
|
|
<colspec colname="col1" colwidth="10*"/>
|
|
<colspec colname="col2" colwidth="1*"/>
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
<entry>Partial Mode</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>mode</primary>
|
|
<secondary>statistical</secondary>
|
|
</indexterm>
|
|
<function>mode</function> () <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <type>anyelement</type> )
|
|
<returnvalue>anyelement</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the <firstterm>mode</firstterm>, the most frequent
|
|
value of the aggregated argument (arbitrarily choosing the first one
|
|
if there are multiple equally-frequent values). The aggregated
|
|
argument must be of a sortable type.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>percentile</primary>
|
|
<secondary>continuous</secondary>
|
|
</indexterm>
|
|
<function>percentile_cont</function> ( <parameter>fraction</parameter> <type>double precision</type> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <type>double precision</type> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>percentile_cont</function> ( <parameter>fraction</parameter> <type>double precision</type> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <type>interval</type> )
|
|
<returnvalue>interval</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the <firstterm>continuous percentile</firstterm>, a value
|
|
corresponding to the specified <parameter>fraction</parameter>
|
|
within the ordered set of aggregated argument values. This will
|
|
interpolate between adjacent input items if needed.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>percentile_cont</function> ( <parameter>fractions</parameter> <type>double precision[]</type> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <type>double precision</type> )
|
|
<returnvalue>double precision[]</returnvalue>
|
|
</para>
|
|
<para role="func_signature">
|
|
<function>percentile_cont</function> ( <parameter>fractions</parameter> <type>double precision[]</type> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <type>interval</type> )
|
|
<returnvalue>interval[]</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes multiple continuous percentiles. The result is an array of
|
|
the same dimensions as the <parameter>fractions</parameter>
|
|
parameter, with each non-null element replaced by the (possibly
|
|
interpolated) value corresponding to that percentile.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>percentile</primary>
|
|
<secondary>discrete</secondary>
|
|
</indexterm>
|
|
<function>percentile_disc</function> ( <parameter>fraction</parameter> <type>double precision</type> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <type>anyelement</type> )
|
|
<returnvalue>anyelement</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the <firstterm>discrete percentile</firstterm>, the first
|
|
value within the ordered set of aggregated argument values whose
|
|
position in the ordering equals or exceeds the
|
|
specified <parameter>fraction</parameter>. The aggregated
|
|
argument must be of a sortable type.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<function>percentile_disc</function> ( <parameter>fractions</parameter> <type>double precision[]</type> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <type>anyelement</type> )
|
|
<returnvalue>anyarray</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes multiple discrete percentiles. The result is an array of the
|
|
same dimensions as the <parameter>fractions</parameter> parameter,
|
|
with each non-null element replaced by the input value corresponding
|
|
to that percentile.
|
|
The aggregated argument must be of a sortable type.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<indexterm>
|
|
<primary>hypothetical-set aggregate</primary>
|
|
<secondary>built-in</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
Each of the <quote>hypothetical-set</quote> aggregates listed in
|
|
<xref linkend="functions-hypothetical-table"/> is associated with a
|
|
window function of the same name defined in
|
|
<xref linkend="functions-window"/>. In each case, the aggregate's result
|
|
is the value that the associated window function would have
|
|
returned for the <quote>hypothetical</quote> row constructed from
|
|
<replaceable>args</replaceable>, if such a row had been added to the sorted
|
|
group of rows represented by the <replaceable>sorted_args</replaceable>.
|
|
For each of these functions, the list of direct arguments
|
|
given in <replaceable>args</replaceable> must match the number and types of
|
|
the aggregated arguments given in <replaceable>sorted_args</replaceable>.
|
|
Unlike most built-in aggregates, these aggregates are not strict, that is
|
|
they do not drop input rows containing nulls. Null values sort according
|
|
to the rule specified in the <literal>ORDER BY</literal> clause.
|
|
</para>
|
|
|
|
<table id="functions-hypothetical-table">
|
|
<title>Hypothetical-Set Aggregate Functions</title>
|
|
<tgroup cols="2">
|
|
<colspec colname="col1" colwidth="10*"/>
|
|
<colspec colname="col2" colwidth="1*"/>
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
<entry>Partial Mode</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>rank</primary>
|
|
<secondary>hypothetical</secondary>
|
|
</indexterm>
|
|
<function>rank</function> ( <replaceable>args</replaceable> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <replaceable>sorted_args</replaceable> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the rank of the hypothetical row, with gaps; that is, the row
|
|
number of the first row in its peer group.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>dense_rank</primary>
|
|
<secondary>hypothetical</secondary>
|
|
</indexterm>
|
|
<function>dense_rank</function> ( <replaceable>args</replaceable> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <replaceable>sorted_args</replaceable> )
|
|
<returnvalue>bigint</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the rank of the hypothetical row, without gaps; this function
|
|
effectively counts peer groups.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>percent_rank</primary>
|
|
<secondary>hypothetical</secondary>
|
|
</indexterm>
|
|
<function>percent_rank</function> ( <replaceable>args</replaceable> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <replaceable>sorted_args</replaceable> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the relative rank of the hypothetical row, that is
|
|
(<function>rank</function> - 1) / (total rows - 1).
|
|
The value thus ranges from 0 to 1 inclusive.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>cume_dist</primary>
|
|
<secondary>hypothetical</secondary>
|
|
</indexterm>
|
|
<function>cume_dist</function> ( <replaceable>args</replaceable> ) <literal>WITHIN GROUP</literal> ( <literal>ORDER BY</literal> <replaceable>sorted_args</replaceable> )
|
|
<returnvalue>double precision</returnvalue>
|
|
</para>
|
|
<para>
|
|
Computes the cumulative distribution, that is (number of rows
|
|
preceding or peers with hypothetical row) / (total rows). The value
|
|
thus ranges from 1/<parameter>N</parameter> to 1.
|
|
</para></entry>
|
|
<entry>No</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<table id="functions-grouping-table">
|
|
<title>Grouping Operations</title>
|
|
<tgroup cols="1">
|
|
<thead>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
Function
|
|
</para>
|
|
<para>
|
|
Description
|
|
</para></entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry role="func_table_entry"><para role="func_signature">
|
|
<indexterm>
|
|
<primary>GROUPING</primary>
|
|
</indexterm>
|
|
<function>GROUPING</function> ( <replaceable>group_by_expression(s)</replaceable> )
|
|
<returnvalue>integer</returnvalue>
|
|
</para>
|
|
<para>
|
|
Returns a bit mask indicating which <literal>GROUP BY</literal>
|
|
expressions are not included in the current grouping set.
|
|
Bits are assigned with the rightmost argument corresponding to the
|
|
least-significant bit; each bit is 0 if the corresponding expression
|
|
is included in the grouping criteria of the grouping set generating
|
|
the current result row, and 1 if it is not included.
|
|
</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
The grouping operations shown in
|
|
<xref linkend="functions-grouping-table"/> are used in conjunction with
|
|
grouping sets (see <xref linkend="queries-grouping-sets"/>) to distinguish
|
|
result rows. The arguments to the <literal>GROUPING</literal> function
|
|
are not actually evaluated, but they must exactly match expressions given
|
|
in the <literal>GROUP BY</literal> clause of the associated query level.
|
|
For example:
|
|
<screen>
|
|
<prompt>=></prompt> <userinput>SELECT * FROM items_sold;</userinput>
|
|
make | model | sales
|
|
-------+-------+-------
|
|
Foo | GT | 10
|
|
Foo | Tour | 20
|
|
Bar | City | 15
|
|
Bar | Sport | 5
|
|
(4 rows)
|
|
|
|
<prompt>=></prompt> <userinput>SELECT make, model, GROUPING(make,model), sum(sales) FROM items_sold GROUP BY ROLLUP(make,model);</userinput>
|
|
make | model | grouping | sum
|
|
-------+-------+----------+-----
|
|
Foo | GT | 0 | 10
|
|
Foo | Tour | 0 | 20
|
|
Bar | City | 0 | 15
|
|
Bar | Sport | 0 | 5
|
|
Foo | | 1 | 30
|
|
Bar | | 1 | 20
|
|
| | 3 | 50
|
|
(7 rows)
|
|
</screen>
|
|
Here, the <literal>grouping</literal> value <literal>0</literal> in the
|
|
first four rows shows that those have been grouped normally, over both the
|
|
grouping columns. The value <literal>1</literal> indicates
|
|
that <literal>model</literal> was not grouped by in the next-to-last two
|
|
rows, and the value <literal>3</literal> indicates that
|
|
neither <literal>make</literal> nor <literal>model</literal> was grouped
|
|
by in the last row (which therefore is an aggregate over all the input
|
|
rows).
|
|
</para>
|
|
|
|
</sect1>
|