MSSQL 存储过程实现更新，如果要更新的字段内容为空，则该字段不作变更，只更新其他字段
一项目有这个需求，顺便将代码贴上，共同学习。
/****** 定义输入参数 ******/
ALTERproc[dbo].[upkeywords]
@inkeyvalnvarchar(100),
@inkeycompeteint,
@inkeyincludeint,
@inKeyIDint
as
DECLARE
/****** 定义变量 ******/
@keyvalnvarchar(100),
@keycompeteint,
@keyincludeint,
@KeyIDint
/****** 给变量赋原来的值 ******/
set@keyval=(select KeyVal from Keywords where KeyID=@inKeyID)
set@keycompete=(select keycompete from Keywords where KeyID=@inKeyID)
set@keyinclude=(select keyinclude from Keywords where KeyID=@inKeyID)
/****** 如果传入的参数是NULL，就将原来的值还给它 ******/
update Keywords set
KeyVal=ISNULL(@inkeyval,@keyval),
keycompete=ISNULL(@inkeycompete,@keycompete),
keyinclude=ISNULL(@inkeyinclude,@keyinclude)
where KeyID=@inKeyID
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