rdelaage
/
postgresql
mirror of https://git.postgresql.org/git/postgresql.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Marginal editorial improvements for array_agg patch documentation.

This commit is contained in:
Tom Lane 2008-11-13 23:01:09 +00:00
parent 312d51798f
commit c23b6fa7b5
1 changed files with 11 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
doc/src/sgml/func.sgml
View File

@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.458 2008/11/13 15:59:50 petere Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.459 2008/11/13 23:01:09 tgl Exp $ -->
<chapter id="functions">
<title>Functions and Operators</title>
@ -8387,8 +8387,8 @@ SELECT xmlagg(x) FROM test;
</para>
<para>
The influence the order of the concatenation, something like the
following approach to sort the input values can be used:
To determine the order of the concatenation, something like the
following approach can be used:
<screen><![CDATA[
SELECT xmlagg(x) FROM (SELECT * FROM test ORDER BY y DESC) AS tab;
@ -9772,19 +9772,19 @@ SELECT count(*) FROM sometable;
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. In the current
implementation, the order of the concatenation is in principle
undefined. Making the input values to be sorted in some other way
implementation, the order of the input is in principle unspecified.
Supplying the input values from a sorted subquery
will usually work, however. For example:
<screen><![CDATA[
SELECT xmlagg(x) FROM (SELECT * FROM test ORDER BY y DESC) AS tab;
SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
]]></screen>
But this approach is not guaranteed to work in all situations, and
it is not strictly SQL-conforming. A future version of PostgreSQL
might provide an additional feature to control the order in a
better-defined way (<literal>xmlagg(expr ORDER BY expr, expr,
...</literal>).
But this syntax is not allowed in the SQL standard, and is
not portable to other database systems. A future version of
<productname>PostgreSQL</> might provide an additional feature to control
the order in a better-defined way (<literal>xmlagg(expr ORDER BY expr, expr,
...)</literal>).
</para>
<para>