Question

A little rusty, but I would like to return all the Email in the Customers table which are not found in the MailingList table, So I’m using this query, but its taking a bit longer than expected. Is there any other type of logic I can use to make it go faster (Instead of ie M.Email <> C.Email ?

 SELECT DISTINCT C.Email FROM CUSTOMERS C
 INNER JOIN MailingList M ON M.Email <> C.Email
 GROUP BY C.Email

Answer 1

You could do something like this:

SELECT DISTINCT C.Email FROM CUSTOMERS C
LEFT OUTER JOIN MailingList M ON M.Email = C.Email
WHERE M.Email is null

I don’t think the grouping is necessary for either query.