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Doc patch that adds an example of a correllated UPDATE.

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David Fetter
This commit is contained in:
Bruce Momjian 2006-01-19 23:09:42 +00:00
parent 807cb000f6
commit cd5d464e9f
1 changed files with 19 additions and 1 deletions
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doc/src/sgml/ref/update.sgml
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@ -1,5 +1,5 @@
<!-- <!--
$PostgreSQL: pgsql/doc/src/sgml/ref/update.sgml,v 1.33 2005/10/12 23:19:22 tgl Exp $ $PostgreSQL: pgsql/doc/src/sgml/ref/update.sgml,v 1.34 2006/01/19 23:09:42 momjian Exp $
PostgreSQL documentation PostgreSQL documentation
--> -->
@ -205,14 +205,32 @@ UPDATE employees SET sales_count = sales_count + 1 FROM accounts
WHERE accounts.name = 'Acme Corporation' WHERE accounts.name = 'Acme Corporation'
AND employees.id = accounts.sales_person; AND employees.id = accounts.sales_person;
</programlisting> </programlisting>
</para>
<para>
Perform the same operation, using a sub-select in the Perform the same operation, using a sub-select in the
<literal>WHERE</literal> clause: <literal>WHERE</literal> clause:
<programlisting> <programlisting>
UPDATE employees SET sales_count = sales_count + 1 WHERE id = UPDATE employees SET sales_count = sales_count + 1 WHERE id =
(SELECT sales_person FROM accounts WHERE name = 'Acme Corporation'); (SELECT sales_person FROM accounts WHERE name = 'Acme Corporation');
</programlisting> </programlisting>
</para>
<para>
Now that all the papers are signed, update the most recently closed
deal of the travelling salesperson who closed the Rocket Powered
Skates deal with the Acme Corporation.
<programlisting>
UPDATE employees SET last_closed_deal = deal.id
FROM accounts JOIN deals ON (account.id = deal.account_id)
WHERE deal.employee_id = employees.id
AND deal.name = 'Rocket Powered Skates'
AND accounts.name = 'Acme Corporation'
ORDER BY deal.signed_date DESC LIMIT 1;
</programlisting>
</para>
<para>
Attempt to insert a new stock item along with the quantity of stock. If Attempt to insert a new stock item along with the quantity of stock. If
the item already exists, instead update the stock count of the existing the item already exists, instead update the stock count of the existing
item. To do this without failing the entire transaction, use savepoints. item. To do this without failing the entire transaction, use savepoints.