一直都认为是in的效率要高，但是这次确有点蒙圈。
SELECT * FROM runinfo WHERE status in (0,2,1,3,4,7,9,10);
这个查询的效率是，经常是1秒多。
mysql> SELECT * FROM runinfo WHERE status in (0,2,1,3,4,7,9,10);
106 rows in set (1.20 sec)
替换成下面这种写法之后，
SELECT * FROM runinfo WHERE status = 0
union
SELECT * FROM runinfo WHERE status = 1
union
SELECT * FROM runinfo WHERE status = 2
union
SELECT * FROM runinfo WHERE status = 3
union
SELECT * FROM runinfo WHERE status = 4
union
SELECT * FROM runinfo WHERE status = 7
union
SELECT * FROM runinfo WHERE status = 9
union
SELECT * FROM runinfo WHERE status = 10
效率有很大的提升。
mysql>
108 rows in set (0.02 sec)
具体的原因我也说不上来，其中status字段有建索引，这个字段会有一些更新。
先做记录，慢慢再搞清楚这件事情吧。