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<chapter id="functions">

<title>Functions and Operators</title>

<literal>IS NULL</> is true when the row expression itself is null

or when all the row's fields are null, while

<literal>IS NOT NULL</> is true when the row expression itself is non-null

and all the row's fields are non-null.

and all the row's fields are non-null. Because of this behavior,

<literal>IS NULL</> and <literal>IS NOT NULL</> do not always return

inverse results for row-valued expressions, i.e. a row-valued

expression that contains both NULL and non-null values will return false

for both tests.

This definition conforms to the SQL standard, and is a change from the

inconsistent behavior exhibited by <productname>PostgreSQL</productname>

versions prior to 8.2.