Select users belonging only to particular departments

Question

I have the following table with two fields namely a and b as shown below:

create table employe
(
    empID varchar(10),
    department varchar(10)
);
         


        

Answer 1

You can use GROUP BY with having like this. SQL Fiddle

SELECT empID 
FROM employe
GROUP BY empID
HAVING SUM(CASE WHEN department= 'Y' THEN 1 ELSE 0 END) > 0
AND SUM(CASE WHEN department= 'Z' THEN 1 ELSE 0 END) > 0
AND SUM(CASE WHEN department NOT IN('Y','Z') THEN 1 ELSE 0 END) = 0

Without GROUP BY and Having

SELECT empID 
FROM employe E1
WHERE (SELECT COUNT(DISTINCT department) FROM employe E2 WHERE E2.empid = E1.empid and  department IN ('Z','Y')) = 2
EXCEPT
SELECT empID 
FROM employe
WHERE department NOT IN ('Z','Y')

If you want to use any of the above query with other tables using a join you can use CTE or a derived table like this.

;WITH CTE AS 
(

    SELECT empID 
    FROM employe
    GROUP BY empID
    HAVING SUM(CASE WHEN department= 'Y' THEN 1 ELSE 0 END) > 0
    AND SUM(CASE WHEN department= 'Z' THEN 1 ELSE 0 END) > 0
    AND SUM(CASE WHEN department NOT IN('Y','Z') THEN 1 ELSE 0 END) = 0
)
SELECT cols from CTE join othertable on col_cte = col_othertable