Gary Stainburn <gary.stainburn@ringways.co.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
