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

Try this,

SELECT  a.empId
FROM    employe a
        INNER JOIN
        (
            SELECT  empId
            FROM    employe 
            WHERE   department IN ('X', 'Y', 'Z')
            GROUP   BY empId
            HAVING  COUNT(*) = 3
           )b ON a.empId = b.empId
GROUP BY a.empId

Count must based on number of conditions.