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Commita84171b

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Add documentation clarification for IS [NOT] NULL and row-valued
expressions.
1 parent347dd6a commita84171b

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‎doc/src/sgml/func.sgml

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<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.427 2008/04/04 18:45:36 tgl Exp $ -->
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<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.428 2008/04/07 00:51:27 momjian Exp $ -->
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<chapter id="functions">
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<title>Functions and Operators</title>
@@ -344,7 +344,11 @@
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<literal>IS NULL</> is true when the row expression itself is null
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or when all the row's fields are null, while
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<literal>IS NOT NULL</> is true when the row expression itself is non-null
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and all the row's fields are non-null.
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and all the row's fields are non-null. Because of this behavior,
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<literal>IS NULL</> and <literal>IS NOT NULL</> do not always return
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inverse results for row-valued expressions, i.e. a row-valued
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expression that contains both NULL and non-null values will return false
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for both tests.
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This definition conforms to the SQL standard, and is a change from the
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inconsistent behavior exhibited by <productname>PostgreSQL</productname>
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versions prior to 8.2.

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