普通while循环
1 循环5来修改学生信息
循环遍历修改记录
DECLARE @i int
set @i=0
while @i<5
BEGIN
update Student set demo = demo+5 WHERE Uid=@i
set @i=@i +1
--PRINT @i
END
2 游标循环(没有事务)
----游标循环(没有事务)
BEGIN
DECLARE @a INT,@error INT
DECLARE @temp NVARCHAR(50)
SET @a=1
SET @error=0
-----申明游标为uid
DECLARE order_cursor CURSOR
FOR (SELECT [Uid] FROM Student)
-----打开游标
OPEN order_cursor
---- 开始循环游标变量
FETCH NEXT FROM order_cursor INTO @temp
WHILE @@FETCH_STATUS=0 -----返回被FETCH语句执行的最后游标的状态
BEGIN
UPDATE student SET Age=15+@a,demo=@a WHERE uid=@temp
SET @a=@a+1
SET @error=@error+@@ERROR ------记录每次运行sql后是否正确 0正确
FETCH NEXT FROM order_cursor INTO @temp -----转到下一个游标,没有会死循环
END
CLOSE order_cursor ----关闭游标
DEALLOCATE order_cursor ---释放游标
END
3 包含事务
---游标循环遍历--
BEGIN
DECLARE @a INT ,@error INT
DECLARE @temp VARCHAR(50)
SET @a=1
SET @error=0
BEGIN TRAN
DECLARE order_cursor CURSOR
FOR(SELECT uid FROM student)
OPEN order_cursor
FETCH NEXT FROM order_cursor INTO @temp
WHILE @@FETCH_STATUS=0 ---返回被fetch语句执行的最后游标的状态
BEGIN
UPDATE student SET age=40+@a,demo=@a WHERE uid=@temp
SET @a=@a+1
SET @error=@error+@@ERROR
FETCH NEXT FROM order_cursor INTO @temp ----转到下一个游标
END
IF(@error=0)
BEGIN
COMMIT TRAN
END
ELSE
BEGIN
ROLLBACK TRAN
END
CLOSE order_cursor
DEALLOCATE order_cursor
END