group by的SQL语句

有一张项目表

CREATE TABLE [ProjectTable] (
[ProjectID] NVARCHAR(16) NOT NULL,
[ProjectName] NVARCHAR(20) NOT NULL ON CONFLICT REPLACE DEFAULT Null,
[DeviceID] INTEGER(16) NOT NULL ON CONFLICT FAIL,
[Description] NVARCHAR(255) NOT NULL ON CONFLICT REPLACE DEFAULT 工程描述);

使用一下的sql语句

select 
distinct 
a.[ProjectID],
a.[ProjectName] 
from 
projecttable as a

得出的结果为

其实想要的数据，只是不同的ProjectID所对应的ProjectName

修改sql语句为

select 
distinct 
a.[ProjectID],
a.[ProjectName] 
from 
projecttable as a
group by a.[ProjectID]

group by的SQL语句

原文：http://www.cnblogs.com/chucklu/p/4522906.html