取每组数据的第一条记录的SQL语句
2011-04-15
取每组数据的第一条记录的SQL语句
-- 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
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
还有一种写法：
SELECT * FROM JobLog A
EXISTS
( select JobLogId in from JobLog
where JobLog.FunctionId=A.FunctionId and JobLog.JobLogId <A.JobLogId
)
select * from tb where JobLogId in (select min(JobLogId) from tb group by FunctionId);
