sql - 无法在 where 子句中使用临时列？

Question

select  cast(de.ApprovalOrder AS VARCHAR(32)) 
            + cast(de.EntityCode AS VARCHAR(32)) 
            + isnull(cast(de.DelegationCode AS VARCHAR(32)), '') as 'RowID' ,
            *
from    workflow.delegation_engine de
where   RowID <> NULL

当我尝试执行以下命令时，我收到错误:

Msg 207, Level 16, State 1, Line 13 Invalid column name 'RowID'.

只是想知道如何引用这个临时专栏？我搜索了之前的帖子，其中建议使用“having”，但这似乎也不起作用。

Answer 1

一种解决方案是对整个语句进行子选择，对其结果应用 where 子句

select  *
from    (
          select  cast(de.ApprovalOrder AS VARCHAR(32)) 
                  + cast(de.EntityCode AS VARCHAR(32)) 
                  + isnull(cast(de.DelegationCode AS VARCHAR(32)), '') as 'RowID'
                  , *
          from    workflow.delegation_engine de
        ) de 
where   de.RowID IS NOT NULL

<小时/>

另一种解决方案可能是在 WHERE 子句中重复整个子句

select  cast(de.ApprovalOrder AS VARCHAR(32)) 
        + cast(de.EntityCode AS VARCHAR(32)) 
        + isnull(cast(de.DelegationCode AS VARCHAR(32)), '') as 'RowID' ,
        *
from    workflow.delegation_engine de
where   cast(de.ApprovalOrder AS VARCHAR(32)) 
        + cast(de.EntityCode AS VARCHAR(32)) 
        + isnull(cast(de.DelegationCode AS VARCHAR(32)), '') IS NOT NULL

<小时/>

或者您可以测试每个单独的字段是否为 NULL

select  cast(de.ApprovalOrder AS VARCHAR(32)) 
        + cast(de.EntityCode AS VARCHAR(32)) 
        + isnull(cast(de.DelegationCode AS VARCHAR(32)), '') as 'RowID' ,
        *
from    workflow.delegation_engine de
where   de.ApprovalOrder IS NOT NULL
        AND de.EntityCode IS NOT NULL