Question

我有这个存储过程

CREATE PROCEDURE spGrabSerial
  @serial nvarchar(16) output
AS
BEGIN
  SET NOCOUNT ON;
  set @serial = (SELECT top 1 serial from tblSerial)
  update tblSerial set InUse = 1 where serial = @serial
END

如何确保没有其他程序在select和update之间抓取相同的序列？

Answer 1

假设SQL Server 2005+，您可以使用OUTPUT子句在一个原子操作中执行此操作（请参阅Using tables as Queues）。

 ;with cte as (
    select top(1) 
      serial, InUse
    from tblSerial with (rowlock, readpast)
    where InUse <> 1
    order by serial
   )
 update cte 
 set InUse = 1 
 output inserted.serial

修改刚刚提醒过一种可以直接分配到output参数而不使用OUTPUT子句的方法。

 with cte as (
    select top(1) 
      serial, InUse
    from tblSerial with (rowlock, readpast)
    where InUse <> 1
    order by serial
   )
 update cte 
 set InUse = 1, @serial = serial

Answer 2

确保在事务隔离级别“可重复读取”中运行它：

set transaction isolation level repeatable read

然后在事务中运行存储过程，它将与其他更改隔离。

在SQL Server中返回值并更新行而没有“干扰”

2 个答案: