利用带关联子查询Update语句更新数据的方法

--1.创建测试表
  create TABLE Table1
  (
    a varchar(10),
    b varchar(10),
    c varchar(10),
    CONSTRAINT [PK_Table1] PRIMARY KEY CLUSTERED
    (
      a ASC
    )
  ) ON [PRIMARY]

  create TABLE Table2
  (
    a varchar(10),
    c varchar(10),
    CONSTRAINT [PK_Table2] PRIMARY KEY CLUSTERED
    (
      a ASC
    )
  ) ON [PRIMARY]
  GO
  --2.创建测试数据
  Insert into Table1 values('赵','asds',null)
  Insert into Table1 values('钱','asds','100')
  Insert into Table1 values('孙','asds','80')
  Insert into Table1 values('李','asds',null)

  Insert into Table2 values('赵','90')
  Insert into Table2 values('钱','100')
  Insert into Table2 values('孙','80')
  Insert into Table2 values('李','95')
  GO
  select * from Table1

  --3.通过游标方式更新
  declare @name varchar(10)
  declare @score varchar(10)
  declare mycursor cursor for select a from Table1 where c is null
  open mycursor
  fetch next from mycursor into @name
  while(@@fetch_status = 0)
  BEGIN
    select @score=c from Table2 where a=@name
    update Table1 set c = @score where a = @name
    fetch next from mycursor into @name  
  END
  close mycursor
  deallocate mycursor
  GO
  --4.显示更新后的结果
  select * from Table1
  GO
  --5.删除测试表
  drop TABLE Table1
  drop TABLE Table2

--1.创建测试表
  create TABLE Table1
  (
    a varchar(10),
    b varchar(10),
    c varchar(10),
    CONSTRAINT [PK_Table1] PRIMARY KEY CLUSTERED
    (
      a ASC
    )
  ) ON [PRIMARY]

  create TABLE Table2
  (
    a varchar(10),
    c varchar(10),
    CONSTRAINT [PK_Table2] PRIMARY KEY CLUSTERED
    (
      a ASC
    )
  ) ON [PRIMARY]
  GO
  --2.创建测试数据
  Insert into Table1 values('赵','asds',null)
  Insert into Table1 values('钱','asds','100')
  Insert into Table1 values('孙','asds','80')
  Insert into Table1 values('李','asds',null)

  Insert into Table2 values('赵','90')
  Insert into Table2 values('钱','100')
  Insert into Table2 values('孙','80')
  Insert into Table2 values('李','95')
  GO
  select * from Table1

  --3.通过Update方式更新
  Update Table1 set c = (select c from Table2 where a = Table1.a) where c is null
  GO

  --4.显示更新后的结果
  select * from Table1
  GO
  --5.删除测试表
  drop TABLE Table1
  drop TABLE Table2