From: http://www.postgresql.org/docs/8.2/static/functions-comparison.html
" The ordinary comparison operators yield null (signifying "unknown") when either input is null. Another way to do comparisons is with the IS [ NOT ] DISTINCT FROM construct: expression IS DISTINCT FROM expression expression IS NOT DISTINCT FROM expression For non-null inputs, IS DISTINCT FROM is the same as the <> operator. However, when both inputs are null it will return false, and when just one input is null it will return true. Similarly, IS NOT DISTINCT FROM is identical to = for non-null inputs, but it returns true when both inputs are null, and false when only one input is null. Thus, these constructs effectively act as though null were a normal data value, rather than "unknown"." However, when I do: SELECT 1 IS NOT DISTINCT FROM 2 I get "ERROR: syntax error at or near "DISTINCT"" I can do: SELECT NOT (1 IS DISTINCT FROM 2) What is the problem here? Regards, Collin ---------------------------(end of broadcast)--------------------------- TIP 2: Don't 'kill -9' the postmaster
