Question

I have a simple table “Employees” with this fields:

ID, ParentID, Name

ParentID is Nullable since an employee may have no Manager.
This table has a one-to-many relationship with itself:

ID --one--to--many--> ParentID

Now I want a query which returns this columns:

Name, Count of rows where their ParentID equals to the current row ID (the row is the manager of that rows)

Sample Table:

ID | ParentID | Name
======================
 1 |     0    | John
----------------------
 2 |     1    | Bob
----------------------
 3 |     1    | Alice
----------------------
 4 |     3    | Jack

This way I can find an employee is the manager of how many other employees.
The result should be something like this:

Name  | Count of Employees
==========================
John  |   2
--------------
Bob   |   0
--------------
Alice |   1
--------------
Jack  |   0

How can I achieve this in MS ACCESS 2007?
* I have tried built-in query builder without any success.

Answer 1

So you just want a count of how many employees a manager has?

You will have to join the table to itself. It can be done in the query builder but the SQL statement will be easier to put here.

SELECT [Employees].Name, [Employees].ParentID, [Employees].Name, Count([Employees1].ParentID) AS NoOfEmployees
FROM [Employees] LEFT JOIN [Employees] AS [Employees1] ON [Employees].ID = [Employees1].ParentID
GROUP BY [Employees].ID, [Employees].ParentID, [Employees].Name;

I added the two other columns from the tables and renamed the count column to NoOfEmployees.