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 condition 1:z and y

 select z.empID from (select empID from employe where department = 'z' ) as z
inner join (select empID from employe where department = 'y' )  as y 
on z.empID = y.empID
where z.empID Not in(select empID from employe where department = 'x' ) 

For condition 1:z and x

select z.empID from (select empID from employe where department = 'z' ) as z
inner join (select empID from employe where department = 'x' )  as x 
on z.empID = x.empID
where z.empID Not in(select empID from employe where department = 'y' )

For condition 1:z,y and x

select z.empID from (select empID from employe where department = 'z' ) as z
inner join (select empID from employe where department = 'x' )  as x 
on z.empID = x.empID
inner join (select empID from employe where department = 'y' )  as y on 
y.empID=Z.empID