-- 操作日志表
CREATE
TABLE JobLog -- 操作日志表
(
JobLogId] int
NOT
NULL , -- 主键
FunctionId nvarchar(20)
NULL ,
-- 功能Id
OperateTime datetime
NULL -- 操作时间
) ON
PRIMARY
GO
ALTER
TABLE JobLog
ADD
CONSTRAINT PK_JobLog
PRIMARY
KEY CLUSTERED(JobLogId)
ON PRIMARY
GO
-- 操作日志表的所有记录
SELECT
* FROM JobLog
查询结果:
1 001 2007-11-01
2 001 2007-11-02
3 001 2007-11-03
4 002 2007-11-04
5 002 2007-11-05
6 003 2007-11-06
7 004 2007-11-07
8 004 2007-11-08
9 005 2007-11-09
10 005 2007-11-10
-- 每个功能最后一次操作记录
SELECT
* FROM JobLog A
WHERE JobLogId
in
(SELECT
TOP
1 JobLogId
FROM JobLog
WHERE A.FunctionId
= FunctionId
ORDER
BY OperateTime
DESC
)
查询结果:
3 001 2007-11-03
5 002 2007-11-05
6 003 2007-11-06
8 004 2007-11-08
10 005 2007-11-10
当有大量数据时,上面的语句执行效率很低,数据量超过10万条时,在我的机器上运行了5分钟还没有完成。可以考虑用以下SQL语句:
1. 得到第一条:
SELECT * FROM JobLog a,
(
SELECT FunctionId, MIN(OperateTime) AS OperateTime FROM
JobLog
GROUP BY FunctionId
) b
WHERE a.FunctionId = b.FunctionId AND a.OperateTime = b.OperateTime
2. 得到最后一条:
SELECT * FROM JobLog a,
(
SELECT FunctionId, MAX(OperateTime) AS OperateTime FROM
JobLog
GROUP BY FunctionId
) b
WHERE a.FunctionId = b.FunctionId AND a.OperateTime = b.OperateTime
以上语句在数据量10万条时执行时间近5秒。