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SQL:2008 alternative syntax for LIMIT/OFFSET:

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OFFSET num {ROW|ROWS} FETCH {FIRST|NEXT} [num] {ROW|ROWS} ONLY
This commit is contained in:
Peter Eisentraut
2008-10-22 11:00:34 +00:00
parent e6ae3b5dbf
commit 361bfc3572
6 changed files with 108 additions and 27 deletions
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48
doc/src/sgml/ref/select.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.106 2008/10/07 19:27:04 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.107 2008/10/22 11:00:33 petere Exp $
PostgreSQL documentation
-->
@ -30,7 +30,8 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
[ { UNION | INTERSECT | EXCEPT } [ ALL ] <replaceable class="parameter">select</replaceable> ]
[ ORDER BY <replaceable class="parameter">expression</replaceable> [ ASC | DESC | USING <replaceable class="parameter">operator</replaceable> ] [ NULLS { FIRST | LAST } ] [, ...] ]
[ LIMIT { <replaceable class="parameter">count</replaceable> | ALL } ]
[ OFFSET <replaceable class="parameter">start</replaceable> ]
[ OFFSET <replaceable class="parameter">start</replaceable> [ ROW | ROWS ] ]
[ FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] { ROW | ROWS } ONLY ]
[ FOR { UPDATE | SHARE } [ OF <replaceable class="parameter">table_name</replaceable> [, ...] ] [ NOWAIT ] [...] ]
where <replaceable class="parameter">from_item</replaceable> can be one of:
@ -150,7 +151,7 @@ and <replaceable class="parameter">with_query</replaceable> is:
<listitem>
<para>
If the <literal>LIMIT</literal> or <literal>OFFSET</literal>
If the <literal>LIMIT</literal> (or <literal>FETCH FIRST</literal>) or <literal>OFFSET</literal>
clause is specified, the <command>SELECT</command> statement
only returns a subset of the result rows. (See <xref
linkend="sql-limit" endterm="sql-limit-title"> below.)
@ -891,6 +892,24 @@ OFFSET <replaceable class="parameter">start</replaceable>
class="parameter">count</replaceable> rows to be returned.
</para>
<para>
SQL:2008 introduced a different syntax to achieve the same thing,
which PostgreSQL also supports. It is:
<synopsis>
OFFSET <replaceable class="parameter">start</replaceable> { ROW | ROWS }
FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] { ROW | ROWS } ONLY
</synopsis>
Both clauses are optional, but if present
the <literal>OFFSET</literal> clause must come before
the <literal>FETCH</literal> clause. <literal>ROW</literal>
and <literal>ROWS</literal> as well as <literal>FIRST</literal>
and <literal>NEXT</literal> are noise words that don't influence
the effects of these clauses. When using expressions other than
constants for the offset or fetch count, parentheses will be
necessary in most cases. If the fetch count is omitted, it
defaults to 1.
</para>
<para>
When using <literal>LIMIT</>, it is a good idea to use an
<literal>ORDER BY</> clause that constrains the result rows into a
@ -1337,13 +1356,30 @@ SELECT distributors.* WHERE distributors.name = 'Westward';
</para>
</refsect2>
<refsect2>
<title><literal>LIMIT</literal> and <literal>OFFSET</literal></title>
<para>
The clauses <literal>LIMIT</literal> and <literal>OFFSET</literal>
are <productname>PostgreSQL</productname>-specific syntax, also
used by <productname>MySQL</productname>. The SQL:2008 standard
has introduced the clauses <literal>OFFSET ... FETCH {FIRST|NEXT}
...</literal> for the same functionality, as shown above
in <xref linkend="sql-limit" endterm="sql-limit-title">, and this
syntax is also used by <productname>IBM DB2</productname>.
(Applications written for <productname>Oracle</productname>
frequently use a workaround involving the automatically
generated <literal>rownum</literal> column, not available in
PostgreSQL, to implement the effects of these clauses.)
</para>
</refsect2>
<refsect2>
<title>Nonstandard Clauses</title>
<para>
The clauses <literal>DISTINCT ON</literal>,
<literal>LIMIT</literal>, and <literal>OFFSET</literal> are not
defined in the SQL standard.
The clause <literal>DISTINCT ON</literal> is not defined in the
SQL standard.
</para>
</refsect2>
</refsect1>

5
doc/src/sgml/ref/select_into.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/select_into.sgml,v 1.41 2008/10/04 21:56:52 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/select_into.sgml,v 1.42 2008/10/22 11:00:34 petere Exp $
PostgreSQL documentation
-->
@ -31,7 +31,8 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
[ { UNION | INTERSECT | EXCEPT } [ ALL ] <replaceable class="parameter">select</replaceable> ]
[ ORDER BY <replaceable class="parameter">expression</replaceable> [ ASC | DESC | USING <replaceable class="parameter">operator</replaceable> ] [ NULLS { FIRST | LAST } ] [, ...] ]
[ LIMIT { <replaceable class="parameter">count</replaceable> | ALL } ]
[ OFFSET <replaceable class="parameter">start</replaceable> ]
[ OFFSET <replaceable class="parameter">start</replaceable> [ ROW | ROWS ] ]
[ FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] { ROW | ROWS } ONLY ]
[ FOR { UPDATE | SHARE } [ OF <replaceable class="parameter">table_name</replaceable> [, ...] ] [ NOWAIT ] [...] ]
</synopsis>
</refsynopsisdiv>

16
doc/src/sgml/ref/values.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/values.sgml,v 1.4 2007/02/01 00:28:19 momjian Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/values.sgml,v 1.5 2008/10/22 11:00:34 petere Exp $
PostgreSQL documentation
-->
@ -23,7 +23,8 @@ PostgreSQL documentation
VALUES ( <replaceable class="PARAMETER">expression</replaceable> [, ...] ) [, ...]
[ ORDER BY <replaceable class="parameter">sort_expression</replaceable> [ ASC | DESC | USING <replaceable class="parameter">operator</replaceable> ] [, ...] ]
[ LIMIT { <replaceable class="parameter">count</replaceable> | ALL } ]
[ OFFSET <replaceable class="parameter">start</replaceable> ]
[ OFFSET <replaceable class="parameter">start</replaceable> [ ROW | ROWS ] ]
[ FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] { ROW | ROWS } ONLY ]
</synopsis>
</refsynopsisdiv>
@ -48,8 +49,10 @@ VALUES ( <replaceable class="PARAMETER">expression</replaceable> [, ...] ) [, ..
<para>
Within larger commands, <command>VALUES</> is syntactically allowed
anywhere that <command>SELECT</> is. Because it is treated like a
<command>SELECT</> by the grammar, it is possible to use the <literal>ORDER
BY</>, <literal>LIMIT</>, and <literal>OFFSET</> clauses with a
<command>SELECT</> by the grammar, it is possible to use
the <literal>ORDER BY</>, <literal>LIMIT</> (or
equivalently <literal>FETCH FIRST</literal>),
and <literal>OFFSET</> clauses with a
<command>VALUES</> command.
</para>
</refsect1>
@ -227,9 +230,10 @@ WHERE ip_address IN (VALUES('192.168.0.1'::inet), ('192.168.0.10'), ('192.168.1.
<title>Compatibility</title>
<para>
<command>VALUES</command> conforms to the SQL standard, except that
<command>VALUES</command> conforms to the SQL standard.
<literal>LIMIT</literal> and <literal>OFFSET</literal> are
<productname>PostgreSQL</productname> extensions.
<productname>PostgreSQL</productname> extensions; see also
under <xref linkend="sql-select" endterm="sql-select-title">.
</para>
</refsect1>