Question

So I’ve got two tables, A and B, I’m trying to find the values that exist in a column in table A that do not exist in a matching column in table B my current code is:

SELECT A.x
FROM A
WHERE A.x NOT IN (SELECT B.x FROM B);

I have also tried:

SELECT A.x
FROM A
WHERE EXISTS NOT (SELECT B.x FROM B);

But when i run the query, nothing is in the table, I know for a fact that there are values in the “x” column of A that are not in the “x” column of B, but there not showing up.

I have a feeling that I’m doing something extremely dumb, or missing the obviously obvious answer, but I’m to tired and I’ve been working on this for to long to care anymore, so cheers for any help =)

Answer 1

Have you tried using an OUTER JOIN?

SELECT A.x
FROM A LEFT OUTER JOIN B ON A.x = B.x
WHERE B.x IS NULL