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Clearify CHECK handling of unknown test values.

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Karl O. Pinc
This commit is contained in:
Bruce Momjian 2004-05-19 23:10:43 +00:00
parent 4da36853ce
commit 24a1fafc8d
1 changed files with 8 additions and 5 deletions
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13
doc/src/sgml/ref/create_table.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/create_table.sgml,v 1.80 2004/03/22 16:18:50 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/create_table.sgml,v 1.81 2004/05/19 23:10:43 momjian Exp $
PostgreSQL documentation
-->
@ -383,10 +383,13 @@ and <replaceable class="PARAMETER">table_constraint</replaceable> is:
<para>
The <literal>CHECK</> clause specifies an expression producing a
Boolean result which new or updated rows must satisfy for an
insert or update operation to succeed. A check constraint
specified as a column constraint should reference that column's
value only, while an expression appearing in a table constraint
may reference multiple columns.
insert or update operation to succeed. Expressions evaluating
to TRUE or UNKNOWN succeed. Should any row of an insert or
update operation produce a FALSE result an error exception is
raised and the insert or update does not alter the database. A
check constraint specified as a column constraint should
reference that column's value only, while an expression
appearing in a table constraint may reference multiple columns.
</para>
<para>