mysql union order by 分别排序问题

两种方式：

第一种：

先各自排序，然后通过临时表嵌套再合并结果，注意排序后面必须加入 limit，否则order by不起作用

SELECT * FROM (SELECT * FROM t1 WHERE id IN (1,3,6) ORDER BY utime DESC limit 5) AS a 
UNION ALL
SELECT * FROM (SELECT * FROM t1 WHERE id IN (2,4,5) ORDER BY utime DESC limit 5) AS b
;
第二种：

通过加入临时列px查出所有结果后，再按px，utime排序

SELECT * FROM(
SELECT 0 AS px,id,NAME,utime FROM (SELECT * FROM t1 WHERE id IN (1,3,6)) AS a 
UNION ALL
SELECT  1 AS px,id,NAME,utime FROM (SELECT * FROM t1 WHERE id IN (2,4,5)  ) AS b
) AS c ORDER BY px,utime DESC