sql 循环语句几种方式(变量循环，游标循环，事务）

原文地址：https://www.cnblogs.com/fm168/p/5464132.html

--第一

declare @orderNum varchar(255)
create table #ttableName(id int identity(1,1),Orders varchar(255))
declare @n int,@rows int

insert #ttableName(orders) select orderNum from FOrders where orderId<50
--select @rows=count(1) from pe_Orders
select @rows =@@rowcount 
set @n=1 
while @n<=@rows
begin
select @orderNum=OrderNum from PE_Orders where OrderNum=(select Orders from #ttableName where id=@n)
print (@OrderNum)
select @n=@n+1
end
drop table #ttableName

 

 

--第二

declare @tmp varchar(50)--临时变量，用来保存游标值
declare y_curr cursor for --申明游标 为orderNum
select orderNum from FOrders where orderId<50
open y_curr --打开游标
fetch next from Y_curr into @tmp ----开始循环游标变量
while(@@fetch_status=0)---返回被 FETCH 语句执行的最后游标的状态，而不是任何当前被连接打开的游标的状态。
begin
print (@tmp)
update FOrders set Functionary+@tmp where orderNum=@tmp --操作数据库
fetch next from y_curr into @tmp --开始循环游标变量
end
close y_curr--关闭游标
deallocate y_curr --释放游标

 

--第三

select orderNum,userName,MoneyTotal into #t from FOrders po 
DECLARE @n int,@error int
--set @n=1 
set @error=0
BEGIN TRAN --申明事务
declare @tmp varchar(50),@userN varchar(50) --临时变量，用来保存游标值
declare y_curr cursor for --申明游标 为orderNum,userName
select orderNum,userName from FOrders where Orderid<50
open y_curr
fetch next from y_curr into @tmp,@userN
while @@fetch_status = 0
BEGIN
select isnull(sum(MoneyTotal),0),orderNum from #t where username=@userN
-- set @n=@n+1
set @error=@error+@@error--记录每次运行sql后 是否正确 0正确
fetch next from y_curr into @tmp,@userN
END
IF @error=0
BEGIN
commit tran --提交
END
ELSE
BEGIN
ROLLBACK TRAN --回滚
END
close y_curr
deallocate y_curr
DROP TABLE #t