TIL, 2017-08-31
- Bunch of stuff on how joins actually work via StackOverflow.
SELECT... LEFT JOIN B ON A.Key = B.key WHERE B.Key is NULL: Select only A that doesn’t exist in B.SELECT... OUTER JOIN B ON A.Key = B.key WHERE A.Key is NULL OR B.Key is NULL.: Select stuff in A and stuff in B, but not stuff in A/B. Assuming key is unique.