Question

I have a MS Access database for employee training and there is a class that each employee is required to have twice a year.

The table for that class looks like this:

EmployeeID  ClassDate   ClassHours
1           1/1/2011        8
1           7/31/2011       7
2           2/1/2011        8
2           8/31/2011       7
3           3/1/2011        8
3           9/30/2011       7   

I want the table to be formated like this:

EmployeeID  ClassDate_1 ClassHours_1    ClassDate_2 ClassHours_2
1           1/1/2011        8           7/31/2011       7
2           2/1/2011        8           8/31/2011       7   
3           3/1/2011        8           9/30/2011       7   

How do I write a query to move the second class date and hour fields to the same row based off the EmployeeID?

I have researched through this site and all the possible solutions appear to be overly complicated for what I am trying to acheive.

Your help is greatly appreciated.

Thanks

Answer 1

You will have to create a query with a sub-select

SELECT
    X.EmployeeID,
    X.d1 AS ClassDate_1, ec1.ClassHours AS ClassHours_1,
    X.d2 AS ClassDate_2, ec2.ClassHours AS ClassHours_2
FROM
    ( (SELECT e.EmployeeID, Min(e.ClassDate) AS d1, Max(e.ClassDate) AS d2
       FROM employee_classes AS e
       GROUP BY e.EmployeeID) AS X
      INNER JOIN employee_classes AS ec1
          ON X.EmployeeID = ec1.EmployeeID AND X.d1 = ec1.ClassDate
    )
    INNER JOIN employee_classes AS ec2
        ON X.EmployeeID = ec2.EmployeeID AND X.d2 = ec2.ClassDate;

---

Alternatively you could store the nested select as a query (let’s call it query1):

SELECT e.EmployeeID, Min(e.ClassDate) AS d1, Max(e.ClassDate) AS d2
FROM employee_classes AS e
GROUP BY e.EmployeeID

and then use it in a second query

SELECT
    X.EmployeeID,
    X.d1 AS ClassDate_1, ec1.ClassHours AS ClassHours_1,
    X.d2 AS ClassDate_2, ec2.ClassHours AS ClassHours_2
FROM
    ( query1 AS X
      INNER JOIN employee_classes AS ec1
          ON X.EmployeeID = ec1.EmployeeID AND X.d1 = ec1.ClassDate
    )
    INNER JOIN employee_classes AS ec2
        ON X.EmployeeID = ec2.EmployeeID AND X.d2 = ec2.ClassDate;

---

It would be much easier if the hours were not displayed

SELECT e.EmployeeID, Min(e.ClassDate) AS ClassDate_1, Max(e.ClassDate) AS ClassDate_2
FROM employee_classes AS e
GROUP BY e.EmployeeID

---

Indeed there is a simpler solution, however it assumes that the table is sorted by EmployeeID and ClassDate. This assumption is not safe, as no natural sort order is guaranteed. Access can “decide” to reorganize the records in a different way at any time.

SELECT
    EmployeeID,
    First(ClassDate) AS ClassDate_1, First(ClassHours) AS ClassHours_1,
    Last(ClassDate) AS ClassDate_2,  Last(ClassHours) AS ClassHours_2
FROM
    employee_classes
GROUP BY
   EmployeeID
ORDER BY
   EmployeeID;

Here again a sub-select can help

SELECT
    EmployeeID,
    First(ClassDate) AS ClassDate_1, First(ClassHours) AS ClassHours_1,
    Last(ClassDate) AS ClassDate_2,  Last(ClassHours) AS ClassHours_2
FROM
    (SELECT * FROM employee_classes ORDER BY EmployeeID, ClassDate)
GROUP BY
   EmployeeID
ORDER BY
   EmployeeID;

Howsoever, either a sub-query or a second query is required.