I don't get why this isn't working:

table1:
table1ID
table2IDs

table2:
table2ID

I want all the records from table2, including the rows that where the table2ID is not in any table2IDs from table1.

SELECT
table2.table2ID
FROM
table2
LEFT JOIN table1
ON table2.table2ID = table1.table2IDs;

The above query only returns records from talbe2 that have a corresponding value in table2IDs, just like an INNER JOIN.

I'm probably missing something simple here...

Bah. Figured it out.

I left out a part where i was checking criteria on table1, and it won't return an "= NULL" row, because there are no NULL records in table2, only in the result set I'm looking for.

what were the table1 criteria you left out? can you show the final query?

Sure. Basically there are 2 additional columns in both tables that determine whether the row is valid or not. We'll call these columns X, and I was looking for a value of 0, so:

SELECT
table2.table2ID
FROM
table2
LEFT JOIN table1
ON table2.table2ID = table1.table2IDs
WHERE table2.X = 0
AND table1.X = 0;

What I was really looking for in this, were the rows in table2 that were not assigned in table1 (I guess I should note I pulled in the ID from table1 as well so I could sort for the nulls), but the join + checking for X=0 eliminated those rows, so taking "AND table1.X = 0" out of the query above made it work.

It's possible I got some invalid rows where the IDs matched, but since I was only looking for the nulls, that was fine.

try this --see the difference? (no, i'm not talking about the word OUTER -- that's optional, and i just always write it out of habit)

with the table1 condition in the ON clause, it behaves differently, too