Blank Table Result - sql

Question

I am having a problem with my database. I have replicated it using adventure works 2014.
I want to show all results where the BusinessEntityID shows more than once. So if a user has been a member of two deparments, their ID will show twice
But this is what I get with the below query.
SELECT Person.FirstName,
Person.LastName,
HumanResources.Department.Name AS CurrentDepartment,
StartDate,
EndDate
FROM AdventureWorks2014.Person.Person
JOIN HumanResources.EmployeeDepartmentHistory
ON HumanResources.EmployeeDepartmentHistory.BusinessEntityID = Person.BusinessEntityID
JOIN HumanResources.Department
ON EmployeeDepartmentHistory.DepartmentID = HumanResources.Department.DepartmentID
GROUP BY Person.BusinessEntityID,
HumanResources.Department.DepartmentID,
Person.FirstName,
Person.LastName,
HumanResources.Department.Name,
StartDate,
EndDate
HAVING COUNT(Person.BusinessEntityID) > 1
ORDER BY Person.LastName, StartDate
I remove the Having I do get returned result(the whole table). So I think I know where the problem is not what it is / how to resolve it.

Answer 1

Im going assume your query works ok and if you dont include the group by will bring all the employees. So you need join with a list of employees with +1 department
JOIN (SELECT P.BusinessEntityID --, COUNT(EDH.DepartmentID) for debug
FROM AdventureWorks2014.Person.Person P
JOIN HumanResources.EmployeeDepartmentHistory EDH
ON P.BusinessEntityID = EDH.BusinessEntityID
GROUP BY P.BusinessEntityID
HAVING COUNT(EDH.DepartmentID) > 1
) as list_of_employees_with_two_or_more
ON AdventureWorks2014.Person.Person.BusinessEntityID =
list_of_employees_with_two_or_more.BusinessEntityID

Answer 2

WITH cte AS (
SELECT Person.FirstName AS FirstName,
Person.LastName AS LastName,
Person.BusinessEntityID AS BusinessEntityID
FROM AdventureWorks2014.Person.Person
INNER JOIN HumanResources.EmployeeDepartmentHistory
ON HumanResources.EmployeeDepartmentHistory.BusinessEntityID = Person.BusinessEntityID
INNER JOIN HumanResources.Department
ON EmployeeDepartmentHistory.DepartmentID = HumanResources.Department.DepartmentID
GROUP BY Person.FirstName,
Person.LastName,
Person.BusinessEntityID
HAVING COUNT(*) > 1
)
SELECT Person.FirstName,
Person.LastName,
HumanResources.Department.Name AS CurrentDepartment,
StartDate,
EndDate
FROM AdventureWorks2014.Person.Person
INNER JOIN HumanResources.EmployeeDepartmentHistory
ON HumanResources.EmployeeDepartmentHistory.BusinessEntityID = Person.BusinessEntityID
INNER JOIN HumanResources.Department
ON EmployeeDepartmentHistory.DepartmentID = HumanResources.Department.DepartmentID
INNER JOIN cte t
ON Person.FirstName = t.FirstName AND
Person.LastName = t.LastName AND
Person.BusinessEntityID = t.BusinessEntityID

Answer 3

You need to do the grouping separately, what I think you really want is people with more than one record in EmployeeDepartmentHistory, e.g.
SELECT BusinessEntityID
FROM HumanResources.EmployeeDepartmentHistory
GROUP BY BusinessEntityID
HAVING COUNT(*) > 1
I think the most efficient way to integrate this into your current query is by using EXISTS:
SELECT p.FirstName,
p.LastName,
d.Name AS CurrentDepartment,
edh.StartDate,
edh.EndDate
FROM Person.Person AS p
JOIN HumanResources.EmployeeDepartmentHistory AS edh
ON edh.BusinessEntityID = p.BusinessEntityID
JOIN HumanResources.Department AS d
ON d.DepartmentID = edh.DepartmentID
WHERE EXISTS
( SELECT 1
FROM HumanResources.EmployeeDepartmentHistory AS edh2
WHERE edh2.BusinessEntityID = p.BusinessEntityID
HAVING COUNT(*) > 1
)
ORDER BY p.LastName, StartDate