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2+ $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.296 2005/11/28 23:18:48 momjian Exp $
33PostgreSQL documentation
44-->
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@@ -7227,16 +7227,23 @@ SELECT ... WHERE CASE WHEN x <> 0 THEN y/x > 1.5 ELSE false END;
72277227 <primary>COALESCE</primary>
72287228 </indexterm>
72297229
7230+ <indexterm>
7231+ <primary>NVL</primary>
7232+ </indexterm>
7233+
7234+ <indexterm>
7235+ <primary>IFNULL</primary>
7236+ </indexterm>
7237+
72307238<synopsis>
72317239<function>COALESCE</function>(<replaceable>value</replaceable> <optional>, ...</optional>)
72327240</synopsis>
72337241
72347242 <para>
72357243 The <function>COALESCE</function> function returns the first of its
72367244 arguments that is not null. Null is returned only if all arguments
7237- are null. This is often useful to substitute a
7238- default value for null values when data is retrieved for display,
7239- for example:
7245+ are null. It is often used to substitute a default value for
7246+ null values when data is retrieved for display, for example:
72407247<programlisting>
72417248SELECT COALESCE(description, short_description, '(none)') ...
72427249</programlisting>
@@ -7246,7 +7253,9 @@ SELECT COALESCE(description, short_description, '(none)') ...
72467253 Like a <token>CASE</token> expression, <function>COALESCE</function> will
72477254 not evaluate arguments that are not needed to determine the result;
72487255 that is, arguments to the right of the first non-null argument are
7249- not evaluated.
7256+ not evaluated. This SQL-standard function provides capabilities similar
7257+ to <function>NVL</> and <function>IFNULL</>, which are used in some other
7258+ database systems.
72507259 </para>
72517260 </sect2>
72527261
@@ -7262,16 +7271,19 @@ SELECT COALESCE(description, short_description, '(none)') ...
72627271</synopsis>
72637272
72647273 <para>
7265- The <function>NULLIF</function> function returns a null value if and only
7266- if <replaceable>value1</replaceable> and
7267- <replaceable>value2</replaceable> are equal. Otherwise it returns
7268- <replaceable>value1</replaceable>. This can be used to perform the
7269- inverse operation of the <function>COALESCE</function> example
7270- given above:
7274+ The <function>NULLIF</function> function returns a null value if
7275+ <replaceable>value1</replaceable> and <replaceable>value2</replaceable>
7276+ are equal; otherwise it returns <replaceable>value1</replaceable>.
7277+ This can be used to perform the inverse operation of the
7278+ <function>COALESCE</function> example given above:
72717279<programlisting>
72727280SELECT NULLIF(value, '(none)') ...
72737281</programlisting>
72747282 </para>
7283+ <para>
7284+ If <replaceable>value1</replaceable> is <literal>(none)</>, return a null,
7285+ otherwise return <replaceable>value1</replaceable>.
7286+ </para>
72757287
72767288 </sect2>
72777289