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Code review for UPDATE SET (columnlist) patch. Make it handle as much

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of the syntax as this fundamentally dead-end approach can, in particular
combinations of single and multi column assignments.  Improve rather
inadequate documentation and provide some regression tests.
This commit is contained in:
Tom Lane
2006-09-03 22:37:06 +00:00
parent 676d1b4e67
commit 091fe03775
4 changed files with 195 additions and 141 deletions
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31
doc/src/sgml/ref/update.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/update.sgml,v 1.39 2006/09/02 20:34:47 momjian Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/update.sgml,v 1.40 2006/09/03 22:37:05 tgl Exp $
PostgreSQL documentation
-->
@ -21,8 +21,8 @@ PostgreSQL documentation
<refsynopsisdiv>
<synopsis>
UPDATE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ [ AS ] <replaceable class="parameter">alias</replaceable> ]
[ SET <replaceable class="PARAMETER">column</replaceable> = { <replaceable class="PARAMETER">expression</replaceable> | DEFAULT } [, ...] |
SET ( <replaceable class="PARAMETER">column</replaceable> [, ...] ) = ( { <replaceable class="PARAMETER">expression</replaceable> | DEFAULT } [, ...] ) [, ...] ]
SET { <replaceable class="PARAMETER">column</replaceable> = { <replaceable class="PARAMETER">expression</replaceable> | DEFAULT } |
( <replaceable class="PARAMETER">column</replaceable> [, ...] ) = ( { <replaceable class="PARAMETER">expression</replaceable> | DEFAULT } [, ...] ) } [, ...]
[ FROM <replaceable class="PARAMETER">fromlist</replaceable> ]
[ WHERE <replaceable class="PARAMETER">condition</replaceable> ]
[ RETURNING * | <replaceable class="parameter">output_expression</replaceable> [ AS <replaceable class="parameter">output_name</replaceable> ] [, ...] ]
@ -251,10 +251,6 @@ UPDATE films SET kind = 'Dramatic' WHERE kind = 'Drama';
<programlisting>
UPDATE weather SET temp_lo = temp_lo+1, temp_hi = temp_lo+15, prcp = DEFAULT
WHERE city = 'San Francisco' AND date = '2003-07-03';
</programlisting>
<programlisting>
UPDATE weather SET (temp_lo, temp_hi, prcp) = (temp_lo+1, temp_lo+15, DEFAULT)
WHERE city = 'San Francisco' AND date = '2003-07-03';
</programlisting>
</para>
@ -268,6 +264,14 @@ UPDATE weather SET temp_lo = temp_lo+1, temp_hi = temp_lo+15, prcp = DEFAULT
</programlisting>
</para>
<para>
Use the alternative column-list syntax to do the same update:
<programlisting>
UPDATE weather SET (temp_lo, temp_hi, prcp) = (temp_lo+1, temp_lo+15, DEFAULT)
WHERE city = 'San Francisco' AND date = '2003-07-03';
</programlisting>
</para>
<para>
Increment the sales count of the salesperson who manages the
account for Acme Corporation, using the <literal>FROM</literal>
@ -316,6 +320,19 @@ COMMIT;
are <productname>PostgreSQL</productname> extensions.
</para>
<para>
According to the standard, the column-list syntax should allow a list
of columns to be assigned from a single row-valued expression, such
as a sub-select:
<programlisting>
UPDATE accounts SET (contact_last_name, contact_first_name) =
(SELECT last_name, first_name FROM salesmen
WHERE salesmen.id = accounts.sales_id);
</programlisting>
This is not currently implemented &mdash; the source must be a list
of independent expressions.
</para>
<para>
Some other database systems offer a <literal>FROM</> option in which
the target table is supposed to be listed again within <literal>FROM</>.