create table employee
( fname char(30),
minit integer,
lname char(30),
ssn varchar(15) primary key,
bdate date,
address varchar(50),
sex char(1),
salary integer,
superssn varchar(15) references employee(ssn),
dno integer);

create table department
( dname varchar(20),
dnumber integer primary key,
mgrssn varchar(15) references employee(ssn),
mgrstartdate date);

alter table employee add constraint fkdepno
foreign key
(dno) references department(dnumber)
initially deferred deferrable;

create table dept_locations
( dnumber integer references department(dnumber),
dlocation varchar(50),
constraint deplocpk primary key(dnumber,dlocation));

create table project
( pname varchar(30),
pnumber integer primary key,
plocation varchar(50),
dnum integer references department(dnumber));

create table works_on
( essn varchar(15) references employee(ssn),
pno integer references project(pnumber),
hours integer,
constraint worksonpk primary key(essn,pno));

create table dependant
( essn varchar(15) references employee(ssn),
dependant_name char(30),
sex char(1),
bdate date,
relationship char(15),
constraint dependpk primary key(essn,dependant_name));