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<chapter id="plpgsql">

<title>Conditional Control: IF statements</title>

<para>

<function>IF</function> statements let you take action

according to certain conditions. PL/pgSQL has three forms of

IF: IF-THEN, IF-THEN-ELSE, IF-THEN-ELSE IF. NOTE: All

PL/pgSQL IF statements need a corresponding <function>END

IF</function> statement. In ELSE-IF statements you need two:

one for the first IF and one for the second (ELSE IF).

<function>IF</function> statements let you execute commands based on

certain conditions. PL/PgSQL has four forms of IF: IF-THEN, IF-THEN-ELSE,

IF-THEN-ELSE IF, IF-THEN-ELSIF-THEN-ELSE. NOTE: All PL/PgSQL IF statements need

a corresponding <function>END IF</function> clause. With ELSE-IF statements,

you need two: one for the first IF and one for the second (ELSE IF).

</para>

<variablelist>

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>

IF-THEN-ELSIF-ELSE

</term>

<listitem>

<para>

IF-THEN-ELSIF-ELSE allows you test multiple conditions

in one statement. Internally it is handled as nested

IF-THEN-ELSE-IF-THEN commands. The optional ELSE

branch is executed when none of the conditions are met.

</para>

<para>

Here is an example:

</para>

<programlisting>

IF number = 0 THEN

result := ''zero'';

ELSIF number &lt; 0 THEN

result := ''negative'';

ELSIF number &gt; 0 THEN

result := ''negative'';

ELSE

-- now it seems to be NULL

result := ''NULL'';

END IF;

</programlisting>

</para>

</listitem>

</varlistentry>

</variablelist>

</sect3>