Question

使用SQL Server

我正在使用以下2个表格，我希望回答以下问题：查找所有员工的最新工资率和更改日期。

表1：EmployeePayHistory

BusinessEntityID
RateChangeDate
率

表2：员工

BusinessEntityID（员工ID）

我制作的SQL语句但不起作用：

SELECT DISTINCT
    e.BusinessEntityID as [Employee], eph.rate
FROM 
    humanresources.employee AS e 
JOIN 
    humanresources.employeepayhistory as eph ON e.BusinessEntityID = eph.BusinessEntityID
GROUP BY 
    e.BusinessEntityID, eph.Rate
HAVING 
    MAX(eph.ratechangedate)

我也尝试过：

SELECT 
    e.BusinessEntityID AS [Employee], eph.rate, 
    MAX(eph.RateChangeDate)
FROM 
    humanresources.employee AS e 
JOIN 
    humanresources.employeepayhistory as eph ON e.BusinessEntityID = eph.BusinessEntityID
GROUP BY 
    E.BusinessEntityID, eph.Rate

我很难理解如何显示最新RateChangeDate每BusinessEntityID。我认为Group By函数和MAX日期可以解决它。有什么建议吗？

Answer 1

根据您的数据库，可能有一个更简单的选项（例如使用row_number）。但是，这是一个join的通用方法：

select e.BusinessEntityID, e.RateChangeDate, e.Rate
from EmployeePayHistory e
    join (select BusinessEntityID, max(RateChangeDate) RateChangeDate
          from EmployeePayHistory
          group by BusinessEntityID) e2 on e.BusinessEntityID = e2.BusinessEntityID 
                                       and e.RateChangeDate = e2.RateChangeDate

如果您的数据库支持window functions，那么这应该有效：

select *
from (
    select *,
       row_number() over (partition by BusinessEntityID order by RateChangeDate desc) as rn
    from EmployeePayHistory 
    ) t
where rn = 1

where子句中的SQL Max（Date）

1 个答案: