David Gauthier <davegauthierpg(at)gmail(dot)com> writes:
> dvdb=# select
> CASE col1
> WHEN null THEN 'z'
> ELSE col1
> END as col1,
> col2
> from foo;
This test is equivalent to "col1 = null" which will always fail.
You could try something like
CASE WHEN col1 IS NULL THEN ... ELSE ... END
Although I think the particular thing you're doing here would
be better solved with COALESCE(col1, 'z').
regards, tom lane