取每组数据的第一条记录的SQL语句

作者：发布时间：2011-04-15 点击：

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

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);

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