多表连接，左连接分组取一条

create table [maomao365.com]
(keChengName nvarchar(30),
 chengJi     decimal(18,1),
 name        nvarchar(10)
 )
 go
 insert into [maomao365.com]
 (keChengName,chengJi,name)values
 ('语文',98,'张三'),
 ('数学',92,'张三'),
 ('语文',90,'李四'),
 ('数学',100,'李四'),
 ('语文',83,'王二'),
 ('数学',98,'王二')
 go
 
 --方式2:使用开窗函数分组排序后，再获取每科的最低分
  
  select * from 
  (
  select row_number()
   over(partition by keChengName  order by chengJi asc ) as keyId 
   ,* from [maomao365.com]
   ) t where t.keyId =1 
   go