sql - 使用 temp 列过滤结果

Question

我的查询是这样的。

select id,name,salary,(salary-2000) AS [Deductedsalary]  
from EmployeeDetails

我想在 where 子句中使用 [Deductedsalary] 列，类似于下面的查询。

select 
    id, name, salary, (salary-2000) AS [Deductedsalary]  
from 
    EmployeeDetails 
where 
    [Deductedsalary] > 5000

注意：我不想使用带有“salary”列的过滤查询

Answer 1

您不能直接执行此操作 - 您必须在基础Salary列上进行过滤，或者使用 CTE 之类的东西：

WITH CTE AS 
(
   SELECT
       id, name, salary, 
       DeductedSalary = salary - 2000
   FROM
       dbo.EmployeeDetails 
)
SELECT 
   id, name, salary, DeductedSalary
FROM 
   CTE
WHERE
   [Deductedsalary] > 5000

Answer 2

您可以使用子查询来定义别名：

select  *
from    (
        select  salary-2000 as deducted_salary
        ,       *
        from 
                EmployeeDetails 
        ) SubQueryAlias
where   Deductedsalary > 5000

Answer 3

另一种方法是

SELECT id,
       name,
       salary,
       DeductedSalary
FROM   EmployeeDetails
CROSS APPLY (SELECT salary-2000) DS(DeductedSalary)
WHERE  DeductedSalary > 5000 

虽然我会用

SELECT id,
       name,
       salary,
       ( salary - 2000 ) AS [Deductedsalary]
FROM   EmployeeDetails
WHERE  [salary] > 7000 

因为这是可预测的（可以使用索引并且会有更好的基数估计）

Answer 4

你可以试试

Select *
    FROM
    (
        select 
          id, name, salary, (salary-2000) AS [Deductedsalary]  
        from 
           EmployeeDetails 

    ) data
    where 
          [Deductedsalary] > 5000