SQL 分组后获取其中一个字段最大值的整条记录

--有id,name,createDate的一张表testTable

--根据name分组，获取每组中createDate最大的那条记录（整条）查询出来

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创建一张表，语句如下：
[sql] view plaincopy

1. CREATE TABLE [dbo].[testTable]
2. (
3. [id] [int] NOT NULL IDENTITY(1, 1),
4. [name] [nchar] (10) COLLATE Chinese_PRC_CI_AS NULL,
5. [counts] [int] NULL,
6. [createDate] [datetime] NULL
7. )
8. GO
9. -- Constraints and Indexes
10. ALTER TABLE [dbo].[testTable] ADD CONSTRAINT [PK_testTable] PRIMARY KEY CLUSTERED ([id])
11. GO

插入测试数据：

1. insert into testTable(id,name,counts,createDate) values(1,'A ',20,'01 14 2011 10:52PM')
2. insert into testTable(id,name,counts,createDate) values(2,'A ',10,'02 14 2011 10:52PM')
3. insert into testTable(id,name,counts,createDate) values(3,'B ',20,'03 14 2011 10:52PM')
4. insert into testTable(id,name,counts,createDate) values(4,'B ',40,'04 14 2011 10:52PM')
5. insert into testTable(id,name,counts,createDate) values(5,'B ',10,'05 14 2011 10:52PM')
6. insert into testTable(id,name,counts,createDate) values(6,'C ',20,'06 14 2011 10:52PM')
7. insert into testTable(id,name,counts,createDate) values(7,'C ',40,'07 14 2011 10:52PM')

查询SQL语句：

1. select * from (
2. select id,name,counts,createDate,row_number() over(partition by name order by createDate desc) rn
3. from testTable
4. ) t where t.rn <=1

结果如下：