On Mon, Dec 12, 2005 at 01:38:37PM +0000, Micha Szelg wrote: > Description: NULL=NULL is false
No, the result is NULL, not false. See "Comparison Operators" in the documentation: http://www.postgresql.org/docs/7.4/interactive/functions-comparison.html "Do not write expression = NULL because NULL is not 'equal to' NULL. (The null value represents an unknown value, and it is not known whether two unknown values are equal.)" You could change the behavior with the transform_null_equals configuration setting, but as the documentation says, "this option is not a general fix for bad programming." It would be better to use standard-conforming expressions such as IS DISTINCT FROM (standard since SQL:1999, as I recall). test=> SELECT NULL = NULL; ?column? ---------- (1 row) test=> SELECT NULL IS DISTINCT FROM NULL; ?column? ---------- f (1 row) -- Michael Fuhr ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
