Multiple and conditions in the same table

Question

Ok I am going to kick myself for this, but I can't figure it out. I am trying to figure out how to find employees which match multiple criteria in the same table.
create table emp
(empno number,
name  varchar2(10))
create table skills
(skill_id   number,
skill_code varchar2(20))
create table emp_skills
(empno    number,
skill_id number,
rating   number)
insert into emp values(1, 'SMITH');
insert into emp values(2, 'JONES');
insert into skills values (1, 'SQL');
insert into skills values (2, 'PLSQL');
insert into skills values (3, 'JAVA');
insert into emp_skills values(1,1, 8);
insert into emp_skills values(1,2, 9);
insert into emp_skills values(1,3, 10);
insert into emp_skills values(2,1,9);
insert into emp_skills values(2,2,2);
insert into emp_skills values(2,3,7);Now I need to come up with a query finding all employees who match all 3 of the following criteria:
1) Have at least a 5 rating in SQL
2) Have at least a 6 rating in PLSQL
3) Have at least a 7 rating in JAVA
So using this I would expect to return only SMITH since his/her skills meet all 3 criteria. I dont want to use OR in my query since I want all 3 to match not just one of them.
I have a feeling I will need to self join the table - but this is going to be part of a dynamic query for APEX where the users can choose the skills and ratings they want employees to adhere to, so I dont know the number of criteria or the exact criteria in advance. But I figure if I can get a proof of concept SQL I can make it work dynamically.
Any ideas are appreciated - sorry for the long post but I figure more detail is better

Answer 1

with es1 as(
select s.skill_code, es.empno, es.rating
from skills s, emp_skills es
where s.skill_id = es.skill_id
/* main */
select e.*
from emp e
where
exists
(select 'x' from es1
where es1.rating >= 5
and es1.skill_code = 'SQL'
and es1.empno = e.empno)
and
exists
(select 'x' from es1
where es1.rating >= 6
and es1.skill_code = 'PLSQL'
and es1.empno = e.empno)
and
exists
(select 'x' from es1
where es1.rating >= 7
and es1.skill_code = 'JAVA'
and es1.empno = e.empno)
-- Addition (Another example)
with es1 as(
select s.skill_code, es.empno, es.rating
from skills s, emp_skills es
where s.skill_id = es.skill_id
/* main */
select e.*
from emp e
where
(select count(distinct es1.skill_code) from es1
where
((es1.rating >= 5 and es1.skill_code = 'SQL')
or
(es1.rating >= 6 and es1.skill_code = 'PLSQL')
or
(es1.rating >= 7 and es1.skill_code = 'JAVA')
and es1.empno = e.empno)
=3;