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Document BETWEEN.

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Peter Eisentraut 2001-02-05 19:21:45 +00:00
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doc/src/sgml/func.sgml
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<!-- $Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.49 2001/01/21 22:02:01 petere Exp $ -->
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.50 2001/02/05 19:21:45 petere Exp $ -->
<chapter id="functions">
<title>Functions and Operators</title>
@ -185,6 +185,29 @@
<literal>3</literal>).
</para>
<para>
In addition to the comparison operators, the special
<token>BETWEEN</token> construct is available.
<synopsis>
<replaceable>a</replaceable> BETWEEN <replaceable>x</replaceable> AND <replaceable>y</replaceable>
</synopsis>
is equivalent to
<synopsis>
<replaceable>a</replaceable> &gt;= <replaceable>x</replaceable> AND <replaceable>a</replaceable> &lt;= <replaceable>y</replaceable>
</synopsis>
Similarly,
<synopsis>
<replaceable>a</replaceable> NOT BETWEEN <replaceable>x</replaceable> AND <replaceable>y</replaceable>
</synopsis>
is equivalent to
<synopsis>
<replaceable>a</replaceable> &lt; <replaceable>x</replaceable> OR <replaceable>a</replaceable> &gt; <replaceable>y</replaceable>
</synopsis>
There is no difference between the two respective forms apart from
the <acronym>CPU</acronym> cycles required to rewrite the first one
into the second one internally.
</para>
<para>
To check whether a value is or is not NULL, use the constructs
<synopsis>