Question

我有一个员工表（ID）和表，当它改变状态（日期，状态，ID（FK））时。我需要显示根据指定日期的状态排序的员工列表

filteredRes.length

我试过任何日期$ My_Date，但我不知道如何修改所有更改，它只检查最后的日期更改

employees  
ID, Name   
1, Jack  
2, Ralf  
3, Jenny  

changes
IDchange, Date, Status, ID
1, 2015-01-01, 2, 1       //Jack started in 2015-1-1 with status 2
2, 2015-03-01, 1, 2       //Ralf started in 2015-3-1 with status 1
3, 2015-04-01, 1, 3       //Jenny started in 2015-4-1 with status 1
4, 2015-08-01, 2, 2       //Ralf change status to 2 in 2015-8-1 
5, 2015-10-01, 3, 2       //Ralf change status to 3 in 2015-10-1
6, 2016-04-01, 4, 1       //Jack change status to 4 in 2016-04-1

Answer 1

您可以使用相关子查询来获得每位员工的status ID：

SELECT ID, Name, (SELECT Status
                  FROM changes AS c
                  WHERE e.ID = c.ID AND date <= ?
                  ORDER BY date DESC LIMIT 1) AS Status
FROM employees AS e
ORDER BY Status, Name ASC

子查询将返回当前员工的状态，该员工更接近参数化日期值。

Answer 2

我们可以使用简单的连接查询来完成。当我们传递date作为参数时，无需计算max(date)，例如：

select e.name, s.date, s.status
from employee e join status s on e.id = s.id
where s.date = ?
order by s.status desc

查找参数并比较其他表中的日期，按参数排序

2 个答案: