(in)Equality operators evaluates to NULL when any of their
arguments are NULL as summarized bellow.
NULL=NULL ==> NULL
1=NULL ==> NULL
1=1 ==> t
1=2 ==> f
I have a case where I need to delete rows from table A for records
that are designated in table B. One of the joined colum can have NULL
values. Therefore I need an operator behaving as follows:
NULL=NULL ==> t
1=NULL ==> NULL (or anything else as long as it is not t)
1=1 ==> t
1=2 ==> f
I replaced the use of the = operator with this expression:
nullif(tabA.col_with_nulls, tabB.col_with_nulls) IS NULL
It works correctly but the intent is not that clear.
Is there a stock replacement operator that would behave like
the second truth table?
Regards,
Bertrand.
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