T-SQL GROUP BY

前段时间，有举过一些函数例子，如SUM,COUNT,MAX,MIN,AVG，当我们调用这些函数进行运算，再想对这些运算结果进行分组，那得需使用GROUP BY来实现。

下面先准备一些数据。创建一个表[RecordHits]，并填充一些数据：

View Code CREATE TABLE RecordHits 
(
    RId NVARCHAR(2),
    DT DATE,
    Hits INT
)
GO

INSERT INTO [dbo].[RecordHits] VALUES
('R1','2011-01-23',30),
('R2','2011-01-23',33),
('R3','2011-01-23',29),
('R4','2011-01-23',31),
('R1','2011-01-24',25),
('R2','2011-01-24',35),
('R3','2011-01-24',43),
('R4','2011-01-24',37),
('R1','2011-01-25',24),
('R2','2011-01-25',40),
('R3','2011-01-25',36),
('R4','2011-01-25',42),
('R1','2011-01-26',36),
('R2','2011-01-26',42),
('R3','2011-01-26',27),
('R4','2011-01-26',33)
GO

下面例子，是对查询出每笔记点击数和进行分组：

SELECT [RId],SUM([Hits]) AS [TotalHits] FROM [dbo].[RecordHits]
GROUP BY [RId]

结果：