diff options
| author | Neil Conway <neilc@samurai.com> | 2004-03-07 01:01:44 +0000 |
|---|---|---|
| committer | Neil Conway <neilc@samurai.com> | 2004-03-07 01:01:44 +0000 |
| commit | ab8faed00d63b4301df0907233fd896724e27351 (patch) | |
| tree | d244511abb49a702d6ec4f9638a493f183cff175 | |
| parent | 565b4f2de57a552ed8db2eb328e89074462f468e (diff) | |
Editorialization of some text discussing 'IS NULL' vs. '= NULL'.
| -rw-r--r-- | doc/src/sgml/func.sgml | 22 |
1 files changed, 12 insertions, 10 deletions
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml index 6c3856d26f7..a26424372a0 100644 --- a/doc/src/sgml/func.sgml +++ b/doc/src/sgml/func.sgml @@ -1,5 +1,5 @@ <!-- -$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.191 2004/03/05 02:41:14 momjian Exp $ +$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.192 2004/03/07 01:01:44 neilc Exp $ PostgreSQL documentation --> @@ -301,20 +301,22 @@ PostgreSQL documentation <literal><replaceable>expression</replaceable> = NULL</literal> because <literal>NULL</> is not <quote>equal to</quote> <literal>NULL</>. (The null value represents an unknown value, - and it is not known whether two unknown values are equal.) + and it is not known whether two unknown values are equal.) This + behavior conforms to the SQL standard. </para> <para> - Some applications may (incorrectly) require that + Some applications may expect that <literal><replaceable>expression</replaceable> = NULL</literal> returns true if <replaceable>expression</replaceable> evaluates to - the null value. To support these applications, the run-time option - <varname>transform_null_equals</varname> can be turned on (e.g., - <literal>SET transform_null_equals TO ON;</literal>). - <productname>PostgreSQL</productname> will then convert - <literal>x = NULL</literal> clauses to - <literal>x IS NULL</literal>. This was - the default behavior in releases 6.5 through 7.1. + the null value. It is highly recommended that these applications + be modified to comply with the SQL standard. However, if that + cannot be done the <varname>transform_null_equals</varname> + configuration variable is available. If it is enabled, + <productname>PostgreSQL</productname> will convert <literal>x = + NULL</literal> clauses to <literal>x IS NULL</literal>. This was + the default behavior in <productname>PostgreSQL</productname> + releases 6.5 through 7.1. </para> <para> |