同时运行的意思是,在同一个UPDATE里面的SET中,无论是VA=3,VB=2,VC=1,@VIN=4 还是@VIN=4,VA=3,VB=2,VC=1,结果都一样---------------------------------------------------------------- -- Author :DBA_HuangZJ(發糞塗牆) -- Date :2014-07-16 10:56:33 -- Version: -- Microsoft SQL Server 2012 - 11.0.5058.0 (X64) -- May 14 2014 18:34:29 -- Copyright (c) Microsoft Corporation -- Enterprise Edition: Core-based Licensing (64-bit) on Windows NT 6.3 <X64> (Build 9600: ) (Hypervisor) -- ---------------------------------------------------------------- --> 测试数据:[huang] if object_id('[huang]') is not null drop table [huang] go create table [huang]([id] int,[va] varchar(1),[vb] varchar(1),[vc] varchar(1)) insert [huang] select 1,'a','b','c' union all select 2,'c','d','e' union all select 3,'e','f','g' --------------开始查询-------------------------- SELECT * FROM huang WHERE id=1UPDATE huang SET VA=4,VC=VB,VB=VA WHERE ID=1SELECT * FROM huang WHERE id=1 ----------------结果---------------------------- /* id va vb vc ----------- ---- ---- ---- 1 a b c(1 行受影响)(1 行受影响)id va vb vc ----------- ---- ---- ---- 1 4 a b */
关键是我用第一种方法在我机器上测试确实实现了啊,所以我才晕了,我也觉得逻辑上第一个方法写完,应该VA,VB,VC的值都一样,都是VA,或者VIN,但确实是对了,例如VA=3,VB=2,VC=1,@VIN=4执行后,确实VA=4,VB=3,VC=2,现在我怕这种语句拿到客户那里会出什么BUG,
-- Author :DBA_HuangZJ(發糞塗牆)
-- Date :2014-07-16 10:56:33
-- Version:
-- Microsoft SQL Server 2012 - 11.0.5058.0 (X64)
-- May 14 2014 18:34:29
-- Copyright (c) Microsoft Corporation
-- Enterprise Edition: Core-based Licensing (64-bit) on Windows NT 6.3 <X64> (Build 9600: ) (Hypervisor)
--
----------------------------------------------------------------
--> 测试数据:[huang]
if object_id('[huang]') is not null drop table [huang]
go
create table [huang]([id] int,[va] varchar(1),[vb] varchar(1),[vc] varchar(1))
insert [huang]
select 1,'a','b','c' union all
select 2,'c','d','e' union all
select 3,'e','f','g'
--------------开始查询--------------------------
SELECT * FROM huang WHERE id=1UPDATE huang SET VA=4,VC=VB,VB=VA WHERE ID=1SELECT * FROM huang WHERE id=1
----------------结果----------------------------
/*
id va vb vc
----------- ---- ---- ----
1 a b c(1 行受影响)(1 行受影响)id va vb vc
----------- ---- ---- ----
1 4 a b
*/