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Make the behavior of HAVING without GROUP BY conform to the SQL spec.

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Formerly, if such a clause contained no aggregate functions we mistakenly
treated it as equivalent to WHERE.  Per spec it must cause the query to
be treated as a grouped query of a single group, the same as appearance
of aggregate functions would do.  Also, the HAVING filter must execute
after aggregate function computation even if it itself contains no
aggregate functions.
This commit is contained in:
Tom Lane
2005-03-10 23:21:26 +00:00
parent 609e32b929
commit 595ed2a855
20 changed files with 385 additions and 238 deletions
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7
doc/src/sgml/query.sgml
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@@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/query.sgml,v 1.43 2005/01/22 22:56:36 momjian Exp $
$PostgreSQL: pgsql/doc/src/sgml/query.sgml,v 1.44 2005/03/10 23:21:20 tgl Exp $
-->
<chapter id="tutorial-sql">
@@ -783,8 +783,9 @@ SELECT city, max(temp_lo)
will be inputs to the aggregates. On the other hand, the
<literal>HAVING</literal> clause always contains aggregate functions.
(Strictly speaking, you are allowed to write a <literal>HAVING</literal>
clause that doesn't use aggregates, but it's wasteful. The same condition
could be used more efficiently at the <literal>WHERE</literal> stage.)
clause that doesn't use aggregates, but it's seldom useful. The same
condition could be used more efficiently at the <literal>WHERE</literal>
stage.)
</para>
<para>

13
doc/src/sgml/ref/select.sgml
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@@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.81 2005/01/22 23:22:19 momjian Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.82 2005/03/10 23:21:20 tgl Exp $
PostgreSQL documentation
-->
@@ -452,6 +452,17 @@ HAVING <replaceable class="parameter">condition</replaceable>
unambiguously reference a grouping column, unless the reference
appears within an aggregate function.
</para>
<para>
The presence of <literal>HAVING</literal> turns a query into a grouped
query even if there is no <literal>GROUP BY</> clause. This is the
same as what happens when the query contains aggregate functions but
no <literal>GROUP BY</> clause. All the selected rows are considered to
form a single group, and the <command>SELECT</command> list and
<literal>HAVING</literal> clause can only reference table columns from
within aggregate functions. Such a query will emit a single row if the
<literal>HAVING</literal> condition is true, zero rows if it is not true.
</para>
</refsect2>
<refsect2 id="sql-select-list">