救助，关于union语句的优化

球球发布于 2008-09-02 11:28， 1073 次点击

请问，下面的这条语句该怎么优化？
Select Count(*) as usercount from (

SELECT UserID FROM IPTV_COOK_PROGRESS where RowTime between '08-08-01' and '08-08-31'

UNION SELECT UserID FROM IPTV_FISH_HISTORY where RowTime between '08-08-01' and '08-08-31'

UNION SELECT UserID FROM IPTV_FIND_HISTORY where RowTime between '08-08-01' and '08-08-31'

UNION SELECT UserID FROM IPTV_QUIZ_HISTORY where RowTime between '08-08-01' and '08-08-31') a

2 回复

bb38522008-09-02 13:13

1 * 改为1
2 union 改为union all
3 between and 改为>= <=
4 RowTime建立索引

球球2008-09-05 02:09

谢谢。我分别在RowTime_UserID，RowTime，UserID上面创建了索引，查询百万条数据，从1万6毫秒提高到2百毫秒以内。