ERROR 1221 (HY000): Incorrect usage of UNION and ORDER BY

union和union all区别

​​UNION​​​会把两个查询语句的结果集合并起来。
​​​union​​​会过滤掉两个结果集中重复的行，而​​union all​​不会过滤掉重复行。

union order

在​​union​​​两个带​​order​​​的​​select​​的时候，会报错。

ERROR 1221 (HY000): Incorrect usage of UNION and ORDER BY

解决方法就是使用括号，把两个​​SELECT​​​括起来。
例如：

(SELECT A,B,C FROM `s` ORDER BY A DESC) 
UNION 
(SELECT A,B,C FROM `r` ORDER BY B DESC);

或用​​SELECT AS TABLE​​

SELECT * FROM 
(SELECT A,B,C FROM `s` ORDER BY A DESC)
 AS t1 
 UNION 
 SELECT A,B,C FROM `r` ORDER BY B DESC;