Question

What is a good way to calculate difference (in a sense what should be added and deleted from one table to get another) between tables in MySQL?

Answer 1

You can also use a left outer join (the first tells you where a row exists in table a and not b, the second vice-versa):

SELECT a.id FROM a LEFT JOIN b ON a.id = b.id WHERE b.id IS NULL SELECT b.id FROM b LEFT JOIN a ON b.id = a.id WHERE a.id IS NULL