从填充表中的列更新未填充表中的列

Question

我已经尝试了这两个。如果我运行Select代码或在第二个查询上使用Select，它会带回我需要的内容。是不是因为一张桌子没有出现？

使用GDev

update tblCustomerPickupTest
set vcAccountNum = (SELECT vcAccountNum 
                    FROM tblCustomerHeaderTest
                    WHERE tblCustomerHeaderTest.vcAccountNum = tblCustomerPickupTest.vcAccountNum)
WHERE vcAccountNum is null
and EXISTS(SELECT vcAccountNum 
            FROM tblCustomerHeaderTest
            WHERE tblCustomerHeaderTest.vcAccountNum = tblCustomerPickupTest.vcAccountNum )


    use GDev 



update CPT
SET   CPT.vcAccountNum = CHT.vcAccountNum
--select *
from tblCustomerHeaderTest CHT
left join tblCustomerPickupTest CPT
on CPT.iCustomerPickupID = CHT.iCustomerID
where CHT.vcAccountNum is not null