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

for If condition is : Z and Y

   SELECT EMPID FROM EMPLOYE WHERE DEPARTMENT='Z'  AND 
   EMPID IN (SELECT EMPID FROM EMPLOYE WHERE DEPARTMENT ='Y')AND
   EMPID NOT IN(SELECT EMPID FROM EMPLOYE WHERE DEPARTMENT NOT IN ('Z','Y'))