Inner Joining 3 Tables to get a Result

I am new to SQL, but I am trying to find all the jobs that Monica (applicant A2) has ALL the skills for (which would be Job ID jo3 and j05.)

This is the script I am using in Oracle:

drop table Jobskills;
drop table Appskills;
drop table Applies;
drop table Applicant;
drop table Skills;
drop table Job;
drop table Company;

create table Company(compid char(5) primary key, compname varchar(20), 
                     comptype varchar(15));
create table Job(jobid char(5) primary key, jobtitle varchar(20),
                 salarylow int, salaryhigh int, location char(10), 
                 compid references Company(compid) on delete cascade);
create table Skills(skillid char(5) primary key, skillname varchar(15));
create table Jobskills(jobid references Job(jobid) on delete cascade, 
                       skillid references Skills(skillid), 
               expertiseneeded int, primary key(jobid,skillid));
create table Applicant(appid char(5) primary key, name varchar(15), 
                       age int, highdegree char(5), expected_salary int) ;
create table AppSkills(appid references Applicant(appid) on delete cascade, 
                       skillid references Skills(skillid), expertise int,
                       primary key(appid, skillid));
create table Applies(jobid references Job(jobid), 
                     appid references Applicant(appid) on delete cascade, 
                     appdate date, decisiondate date, outcome char(10),  
                     primary key(jobid, appid));

rem Initial Company data
insert into Company values('PWC', 'Price Waterhouse', 'consulting');
insert into Company values('MSFT', 'Microsoft', 'software');
insert into Company values('INTL', 'Intel', 'electronics');
insert into Company values('NCR', 'NCR Corp', 'server');
insert into Company values('WPAF', 'WP Air Force', 'defense');
insert into Company values('DLT', 'Deloitte', 'consulting');

rem Initial Job data
insert into Job values('101', 'Programmer', 55000, 60000, 'Redmond', 'MSFT');
insert into Job values('j02', 'Designer', 42000, 45000, 'Redmond', 'MSFT');
insert into Job values('j03', 'SAP impl', 30000, 40000, 'Chicago', 'PWC');
insert into Job values('j04', 'Proj mgmt', 35000, 55000, 'Chicago', 'PWC');
insert into Job values('j05', 'SOX', 60000, 65000, 'Detroit', 'PWC');
insert into Job values('j06', 'db admin', 45000, 50000, 'Dayton', 'NCR');
insert into Job values('j07', 'db designer', 35000, 40000, 'Dayton', 'NCR');
insert into Job values('j08', 'intern', 25000, 28000, 'Dayton', 'NCR');
insert into Job values('j09', 'engineer', 52000, 55000, 'Dayton','WPAF');
insert into Job values('j10', 'dba', 62000, 65000, 'Dayton','WPAF');
insert into Job values('j11', 'hardware dev', 50000, 65000, 'NYC','INTL');
insert into Job values('j12', 'pcb designer', 55000, 68000,'NYC','INTL');
insert into Job values('j13', 'chip designer', 40000, 55000,'Chicago','INTL');
insert into Job values('j14', 'IT', 40000, 60000, 'Dayton', 'DLT');
insert into Job values('j15', 'IT', 50000, 70000, 'Chicago', 'DLT');

rem initial Skills data
insert into Skills values('s1', 'database');
insert into Skills values('s2', 'programming');
insert into Skills values('s3', 'sox');
insert into Skills values('s4', 'project');
insert into Skills values('s5', 'hardware');
insert into Skills values('s6', 'sap');
insert into Skills values('s7', 'analysis');

rem Initial Jobskills data
insert into Jobskills values('101', 's2', 5);
insert into Jobskills values('101', 's7', 4);
insert into Jobskills values('j02', 's2', 3);
insert into Jobskills values('j02', 's7', 5);
insert into Jobskills values('j03', 's6', 5);
insert into Jobskills values('j04', 's7', 4);
insert into Jobskills values('j04', 's4', 5);
insert into Jobskills values('j04', 's2', 2);
insert into Jobskills values('j05', 's3', 5);
insert into Jobskills values('j06', 's1', 5);
insert into Jobskills values('j06', 's2', 3);
insert into Jobskills values('j07', 's1', 4);
insert into Jobskills values('j07', 's7', 3);
insert into Jobskills values('j08', 's1', 2);
insert into Jobskills values('j09', 's2', 4);
insert into Jobskills values('j09', 's4', 4);
insert into Jobskills values('j10', 's4', 3);
insert into Jobskills values('j10', 's1', 5);
insert into Jobskills values('j11', 's5', 3);
insert into Jobskills values('j11', 's4', 3);
insert into Jobskills values('j12', 's5', 5);
insert into Jobskills values('j13', 's1', 4);
insert into Jobskills values('j13', 's2', 5);
insert into Jobskills values('j14', 's7', 4);

rem initial Applicants data
insert into Applicant values('a1', 'Joe', 30, 'MS', 55000);
insert into Applicant values('a2', 'Monica', 25, 'BS', 62000);
insert into Applicant values('a3', 'Jim', 22, 'BS', 45000);
insert into Applicant values('a4', 'Monica', 25, 'BS', 34000);

rem initial Appskills data
insert into Appskills values('a1', 's1', 3);
insert into Appskills values('a1', 's2', 4);
insert into Appskills values('a1', 's4', 4);
insert into Appskills values('a1', 's6', 3);
insert into Appskills values('a1', 's7', 4);
insert into Appskills values('a2', 's2', 3);
insert into Appskills values('a2', 's3', 5);
insert into Appskills values('a2', 's6', 4);
insert into Appskills values('a3', 's4', 3);
insert into Appskills values('a3', 's1', 3);
insert into Appskills values('a3', 's2', 5);

rem Applies
insert into Applies values ('101', 'a1', '01-JAN-06', '08-JAN-06', 'hire');
insert into Applies values ('101', 'a2', '01-JAN-06', '08-JAN-06', 'hire');
insert into Applies values ('j02', 'a2', '01-JAN-06', '08-JAN-06', 'hire');
insert into Applies values ('j04', 'a2', '01-JAN-06', '08-JAN-06', 'hire');
insert into Applies values ('j02', 'a3', '01-JAN-06', '08-JAN-06', 'nohire');
insert into Applies values ('j04', 'a3', '01-JAN-06', '08-JAN-06', 'nohire');
insert into Applies values ('j06', 'a3', '01-JAN-06', '08-JAN-06', 'nohire');

This is my code so far:

SELECT js.jobid
FROM jobskills js INNER JOIN appskills apps 
ON (js.skillid = apps.skillid) INNER JOIN applicant app 
ON (apps.appid = app.appid)
WHERE app.name = 'Monica'
    AND js.skillid = apps.skillid
    AND js.expertiseneeded = apps.expertise

I keep trying to figure out what I might be doing wrong – so anyone has an explanation that can help me figure it out it would be great! I do not want anyone to write the code for me.

This is the output I get:

JOBID
j02  
j05  
j06  

Answer

Jobs for Monica with all the skills needed and when expertise needed is matched with skills.

select distinct jobid from appskills apps inner join applicant app on apps.appid=app.appid 
    inner join jobskills js on apps.skillid=js.skillid where app.name='Monica'
    and not exists (select jobid from jobskills j where js.jobid=j.jobid and js.skillid<>j.skillid)
and js.expertiseneeded=apps.expertise