Question

我有3个表：Employee，Project，ProjectEmployee

Employee有ID和姓名
Project有ID，Name，StartDate，EndDate
ProjectEmployee有ID，EmployeeID，ProjectID

例如：

EMPLOYEE

    ID  |   Name
    ----+-------
    1   |   Amy 
    2   |   Ben 
    3   |   Charlie

PROJECT

    ID  |   Name    |   StartDate   |   EndDate
    ----+-----------+---------------+--------------
    1   |   P01     |   1-Jan-17    |   1-Feb-17
    2   |   P02     |   2-Feb-17    |   20-Feb-17
    3   |   P03     |   15-Mar-17   |   31-Mar-17
    4   |   P04     |   30-Nov-17   |   30-Dec-17

PROJECTEMPLOYEE

    ID  |   EmployeeID  |   ProjectID
    ----+---------------+-------------
    1   |       1       |   1
    2   |       1       |   2
    3   |       1       |   3
    4   |       1       |   4
    5   |       2       |   1
    6   |       2       |   2
    7   |       3       |   1

我想创建一个查询，以找出在项目中工作的总返回员工。例如，有3名员工在P01工作，但在P1的EndDate后180天内只有2名员工在后续项目中工作（将一个项目的EndDate与下一个项目进行比较＆＃39; StartDates）

例如：

对于P01项目，6个月内的后续项目为P02和P03
对于P02项目，6个月内的后续项目为P03
对于P03项目，6个月内的后续项目无

结果应列出所有项目及其员工总数和返回员工总数：

    Project |   TotalEmployees  |   TotalReturningEmployees
    --------+-------------------+-------------------------------------------
    P01     |       3           |   2   (Both Amy and Ben returning)
    P02     |       2           |   1   (Only Amy worked in P03)
    P03     |       1           |   0   (Amy worked in P04, but it's not within 6 months after P03 ended)   
    P04     |       1           |   0

由于我是SQL的新手，我尝试使用MS Access解决此问题。这是我到目前为止所做的，这可行，但只显示一个项目。

SELECT SelectedProject AS Project,
       COUNT(*) AS ReturningEmployees
FROM
(
    SELECT DISTINCT
        ProjectEmployee.EmployeeID
    FROM Project
        INNER JOIN ProjectEmployee
            ON Project.ID = ProjectEmployee.ProjectID
    WHERE (
              (ProjectEmployee.EmployeeID IN (
                                                 SELECT ProjectEmployee.Employeeid
                                                 FROM ProjectEmployee
                                                 WHERE ProjectEmployee.Projectid = SelectedProject
                                             )
              )
              AND ((Project.StartDate)
          BETWEEN
                  (
                      SELECT Project.EndDate FROM Project WHERE Project.id = SelectedProject
                  ) AND (
                  (
                      SELECT Project.EndDate FROM Project WHERE Project.id = SelectedProject
                  ) + 180
                        )
                  )
          )
) AS Returning;

Answer 1

此查询可以完成工作

SELECT p3.ID,
  (
    SELECT COUNT(*) FROM ProjectEmployee p1 WHERE p1.pid = p3.pid
  ), 
  COUNT(p2.pid)
FROM Project p3
LEFT JOIN ProjectEmployee p2 ON p2.ProjectID = p3.ID and p2.EmployeeID IN
  (
    SELECT pe.EmployeeID 
    FROM ProjectEmployee pe 
    WHERE pe.StartYear <= DateAdd(month, 6, p3.EndDate)
  )
GROUP BY p3.ID

SQL返回员工

1 个答案: