MSSQL 插入数据时候，如果存在则更新的方法分享

摘要:
下文讲述mssql中，插入数据时，如果存在则更新,否则就插入数据的方法分享
实验环境:sql server 2017 
mssql中，我们可以采用 merge into 关键字实现此功能，
当两者匹配成功，则运行***语句，否则运行其它语句，达到插入数据时的判断操作，
具体操作方法如下所示: 

create table [maomao365.com]
(keyid int identity,
info varchar(80)
)
go
insert into [maomao365.com]
(info)values('sqlblog'),
('sqlserver'),('maomao365.com')

---merge into实现如果存在，则更新
---如果不存在，则删除
merge into [maomao365.com] a
using (select 2 as keyid_b, 'other' as info_b ) b 
on ( a.keyid = b.keyid_b)

when matched then
update set a.info= b.info_b --更新

when not matched then
insert (info) values(b.info_b); ---插入

go
select * from [maomao365.com]
go
merge into [maomao365.com] a
using (select 20 as keyid_b, 'new info' as info_b ) b 
on ( a.keyid = b.keyid_b)

when matched then
update set a.info= b.info_b --更新

when not matched then
insert (info) values(b.info_b); ---插入
go

select * from [maomao365.com]
go
truncate table [maomao365.com]
drop table [maomao365.com]

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