sql语句使用游标修改表中数据

declare @a varchar(100),@b varchar(100)
declare user_cursor cursor for
select a,b from tableA tab 
open user_cursor
fetch next from user_cursor
into @a,@b
while @@fetch_status=0
begin
update tableA set a=@a where b=@b
fetch next from user_cursor
into @a,@b
end 
CLOSE user_cursor
DEALLOCATE user_cursor

/*游标的使用*/

--定以后直接赋值--
declare test_Cursor Cursor GLOBAL for/*全局游标*/
select*from dbo.tab1

--先定义后赋值--
declare @test_Cursor2 cursor LOCAL for/*局部游标*/
set @test_Cursor2=Cursor for
select*from dbo.tb2

--用GO结束上面的作用域--
go
open text_Cursor
open text_Cursor2