Re: select ..... not in .....

Gary Stainburn <gary(dot)stainburn(at)ringways(dot)co(dot)uk> writes:
> So, who does this select not return the row?

> select v_d_code, v_o_number, v_vin, v_status from vista_details where v_vin
> not in (
> goole(# select substring(w_vin from '(.{11}$)') from walon);

NOT IN with a sub-select that returns any NULL values cannot succeed;
the result is either FALSE (definite match) or NULL (because of the
NULL comparison results).

You could work around that with a COALESCE, but I think a less klugy
and better-performing answer would be to write it as a left join:

select v_d_code, v_o_number, v_vin, v_status from vista_details
left join walon on (v_vin = substring(w_vin from '(.{11}$)'))
where walon.some-never-null-column IS NULL;

The where-clause rejects any actual join matches...

regards, tom lane