set a.KSMC = b.name
from JC_KSXXB a
inner join chisdb_ymyy..zd_unit_code b on a.KSDM = b.code

示例2：

UPDATE A
SET CompanyCode = b.CompanyCode
FROM A a,B b
where a.TaxNumber=b.TaxNumber
and b.sysno is not null
and a.CompanyCode!=b.CompanyCode

示例3：

在UPDATE语句中使用SUM()聚合函数，代码如下：

UPDATE tblUser
SET TotalScore=temp.AllScore
FROM (
    SELECT SUM(s.Score) AllScore,s.UserId
    FROM tblScore AS s 
    GROUP BY s.UserId  
) temp, tblUser
WHERE temp.UserId=tblUser.Id