您可以在 case 语句中使用 END AS 结果来获取更多数据吗？

Question

所以我试图在这个查询中使用最后的结果，然后创建一个新列。 我需要将 PerformanceTotal 与 Total 进行比较，特别是 PerformanceTotal - total = AmountDifference 这样简单的东西，我不知道该怎么做，我在这里有 SQL 查询：

select
    EmployeeNumber,
    Approvals as TotalApprovals,
    base,
    bonus,
    base + bonus as total,
    case
    when Approvals <= 19 then approvals * 50 + 0
    when approvals > 19 and approvals <= 39 then ((approvals - 19) * 70) + (50*19)
    when approvals > 39 and approvals <= 59 then ((approvals - 39) * 80) + (50*19) + (70*20)
    when approvals > 59 and approvals <= 99 then ((approvals - 59) * 90) + (50*19) + (70*20) + (80*20)
    when approvals > 99 then ((approvals - 99) * 100)                    + (50*19) + (70*20) + (80*20) + (90*40)
    end as PerformanceTotal
from
(select
EmployeeNumber,
sum(applicationsapproved) as Approvals,
sum(BaseCalculation) as Base,
sum(BonusCalcuation) as Bonus
from compensation
where EmployeeNumber = '100032' and ActivityYear='2019'
and ApplicationsApproved > 0
group by EmployeeNumber
) as aa

所以，是的，基本上我想使用“PerformanceTotal”结果数据，我不确定如何或是否可能。

谢谢！

Answer 1

您可以围绕已有的内容放置一个外部查询，并在上部查询中进行数学运算，在底部为该结构设置别名。 据我所知，像 Teradata 这样的一些 DBMS 允许内联使用这些列，但不允许使用 SSMS。

select
aaa.PerformanceTotal
, aaa.total
, aaa.PerformanceTotal - aaa.total AS AmountDifference
FROM
(
select
    EmployeeNumber,
    Approvals as TotalApprovals,
    base,
    bonus,
    base + bonus as total,
    case
    when Approvals <= 19 then approvals * 50 + 0
    when approvals > 19 and approvals <= 39 then ((approvals - 19) * 70) + (50*19)
    when approvals > 39 and approvals <= 59 then ((approvals - 39) * 80) + (50*19) + (70*20)
    when approvals > 59 and approvals <= 99 then ((approvals - 59) * 90) + (50*19) + (70*20) + (80*20)
    when approvals > 99 then ((approvals - 99) * 100)                    + (50*19) + (70*20) + (80*20) + (90*40)
    end as PerformanceTotal
from
(select
EmployeeNumber,
sum(applicationsapproved) as Approvals,
sum(BaseCalculation) as Base,
sum(BonusCalcuation) as Bonus
from compensation
where EmployeeNumber = '100032' and ActivityYear='2019'
and ApplicationsApproved > 0
group by EmployeeNumber
) as aa
) as aaa