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<sect2>

<title>Exclusion constraints</title>

<indexterm>

<primary>exclusion constraint</primary>

</indexterm>

<indexterm>

<primary>constraint</primary>

<secondary>exclusion</secondary>

</indexterm>

<para>

Exclusion constraints ensure that if any two rows are compared on

the specified columns or expressions using the specified operators,

at least one of these operator comparisons will be false. The syntax is:

<programlisting>

CREATE TABLE circles (

c circle,

EXCLUDE USING gist (c WITH &amp;&amp;)

);

</programlisting>

</para>

<para>

See also <link linkend="SQL-CREATETABLE-EXCLUDE"><command>CREATE

TABLE ... CONSTRAINT ... EXCLUDE</></link> for details.

</para>

</sect2>