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gravel
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我在sql中运行以下程序时,
select (firstname+lastname)
from accounts
当firstname=null,lastname为某些字符时如‘client'时,
查询的结果却为null,WHY?
当我运行select lastname form accounts 时能得出正确的结果client
select (firstname+lastname)
from accounts
当firstname=null,lastname为某些字符时如‘client'时,
查询的结果却为null,WHY?
当我运行select lastname form accounts 时能得出正确的结果client