MySQL - How to get a list of values in Table A that don't exist in Table B?

Question

**Table A**
1
2
3
4
5
6


**Table B**
2
3
5

How can I select for entry IDs that only exist in Table B? In this example, I\'m looking for a query th

Answer 1

This avoids IN + subquery:

SELECT A.value FROM A
LEFT OUTER JOIN B ON (A.value = B.value)
WHERE B.value IS NULL

Because IN (subquery) isn't optimized as it is executed for each found row in table A