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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2000-12-16 18:33:13 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2000-12-16 18:33:13 +0000 |
| commit | d316f2226738d91e00461f49f6bef16ae178954c (patch) | |
| tree | 11f5be5debe90eae0893044792a9da236230a365 | |
| parent | cf00d59335f2f695b22628239ffe1f99f7db07a7 (diff) | |
| download | postgresql-d316f2226738d91e00461f49f6bef16ae178954c.tar.gz postgresql-d316f2226738d91e00461f49f6bef16ae178954c.zip | |
Add note that COALESCE and NULLIF are shorthand forms of CASE.
| -rw-r--r-- | doc/src/sgml/func.sgml | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml index 5b3012625ea..48bdb2a5e1c 100644 --- a/doc/src/sgml/func.sgml +++ b/doc/src/sgml/func.sgml @@ -1,4 +1,4 @@ -<!-- $Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.41 2000/12/14 22:30:56 petere Exp $ --> +<!-- $Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.42 2000/12/16 18:33:13 tgl Exp $ --> <chapter id="functions"> <title>Functions and Operators</title> @@ -2618,6 +2618,19 @@ SELECT COALESCE(description, short_description, '(none)') ... SELECT NULLIF(value, '(none)') ... </programlisting> </para> + + <tip> + <para> + <function>COALESCE</function> and <function>NULLIF</function> are + just shorthand for <token>CASE</token> expressions. They are actually + converted into <token>CASE</token> expressions at a very early stage + of processing, and subsequent processing thinks it is dealing with + <token>CASE</token>. Thus an incorrect <function>COALESCE</function> or + <function>NULLIF</function> usage may draw an error message that + refers to <token>CASE</token>. + </para> + </tip> + </sect1> |