In MySQL can I return deleted rows after a deletion?

Question

How to return deleted records of following query in MySQL?

DELETE t1
FROM t1
LEFT JOIN t2 on (t1.t2_id = t2.id)
WHERE t2.id IS NULL OR t2.is_valid = false

Background:

$ mysql --version
mysql  Ver 14.14 Distrib 5.6.23, for osx10.8 (x86_64) using  EditLine wrapper

Answer 1

MySQL doesn't have the equivalent of the output or returning clauses provided by other databases. Your best bet is a temporary table:

CREATE TABLE TheDeletedIds as
    SELECT t1.id
    FROM t1 LEFT JOIN
         t2 
         ON t1.t2_id = t2.id
    WHERE t2.id IS NULL OR t2.is_valid = false;

DELETE t1
    FROM t1
    WHERE t1.id IN (SELECT id FROM TheDeletedIds);

Then the table you just created has the ids you want.

Note: It is important to use the newly-created table for the deletion. Otherwise, another thread/process could change the data between the time you capture the ids and the time you delete them.