子查询

不建议使用子查询，能用链接的用链接，子查询影响服务器性能。

SELECT * FROM t1 WHERE column1 = (SELECT column1 FROM t2);

DELETE FROM t1
WHERE s11 > ANY
 (SELECT COUNT(*) /* no hint */ FROM t2
  WHERE NOT EXISTS
   (SELECT * FROM t3
    WHERE ROW(5*t2.s1,77)=
     (SELECT 50,11*s1 FROM t4 UNION SELECT 50,77 FROM
      (SELECT * FROM t5) AS t5)));

https://dev.mysql.com/doc/refman/5.7/en/subqueries.html