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

union和union all差別

​

​UNION​

​​會把兩個查詢語句的結果集合并起來。

​​

​union​

​​會過濾掉兩個結果集中重複的行，而​

​union all​

​不會過濾掉重複行。

union order

在​

​union​

​​兩個帶​

​order​

​​的​

​select​

​的時候，會報錯。

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

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

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;