sql 循环语句几种方式(变量循环,游标循环,事务)

--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
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