从MySQL UNION查询中排除结果

Question

从MySQL UNION中排除结果的正确方法是什么？我正在寻找相当于:

(query1)
UNION
(query2)
UNION
(query3)
EXCEPT
(query4)

Answer 1

SELECT a.* FROM 
(
   SELECT ... FROM table_a
   UNION
   SELECT ... FROM table_b
)a 
WHERE a.x NOT IN (...) 
// or   WHERE NOT EXIST  ....' 
// or   LEFT JOIN table_n ON () WHERE table_n.id IS NULL