Re: How to do EXCEPT with effective SQL?

[Roland Bouman]

Hi,

You could try to write it like this:

SELECT c
FROM Table1 t1
WHERE NOT EXISTS (
SELECT null
FROM Table2 t2
WHERE t1.c = t2.c
)

or like this:


SELECT c
FROM Table1 t1
LEFT JOIN Table2 t2
ON t1.c = t2.c
WHERE t2.c is null

The latter sample in particular could be quite a bit faster.

BTW i trust you do have an index for the column(s) that is (are) compared?

Good luck, and let us know what happened.