If you just need customer id and order id (and nothing from the original orders table), you can simplify it further http://sqlfiddle.com/#!15/7eb3a/10 http://sq

If you just need customer id and order id (and nothing from the original orders table), you can simplify it further http://sqlfiddle.com/#!15/7eb3a/10 http://sqlfiddle.com/#!15/7eb3a/10