php - How to Find Missing Value Between Two Mysql Tables

Question

select userid from cw_users where NOT EXISTS(Select userid from cw_users_data)

The previous query won't do the job of course.

Trying to find only a missing 'userid' from tableb by doing a comparison.

Both tables contain 'userid' and there should be one similar on each. I'm trying to find which one is missing on second table.

Answer 1

Another method

SELECT cw_users.userid FROM cw_users
LEFT JOIN cw_users_data ON cw_users.userid=cw_users_data.userid
WHERE cw_users_data.userid IS NULL;