SQL Server - Adding Primary and Foreign Keys - sql

Question

I have one query that creates several tables, listed below, and a second query that is supposed to add Primary and Foreign keys to each. However, when I try executing my query, I'm greeted with the following error messages:
Msg 1776, Level 16, State 0, Line 2
There are no primary or candidate keys in the referenced table 'DEPARTMENT' that match the referencing column list in the foreign key 'FK__EMPLOYEE__dno__25869641'.
Msg 1750, Level 16, State 0, Line 2
Could not create constraint. See previous errors.
I'm not sure what this means, as I have researched both primary and foreign keys. Can anyone lead me in the right direction as to how to solve this issue? Thanks! :)
CREATE TABLE EMPLOYEE
(
fname varchar(100),
minit char(1),
lname varchar(100),
ssn char(9),
bdate date,
addr varchar(100),
sex char(1),
salary int,
super_ssn char(9),
dno int
);
CREATE TABLE DEPARTMENT
(
dname varchar(100),
dnumber int,
mgr_ssn char(9),
mgr_start_date date
);
CREATE TABLE DEPENDENTS
(
essn char(9),
dependent_name varchar(100),
sex char(1),
bdate date,
relationship varchar(100)
);
CREATE TABLE DEPT_LOCATIONS
(
dnumber int,
dlocation varchar(100)
);
CREATE TABLE PROJECT
(
pname varchar(100),
pnumber int,
plocation varchar(100),
dnum int
);
CREATE TABLE WORKS_ON
(
essn char(9),
pno int,
hrs float
);
ALTER TABLE EMPLOYEE ADD PRIMARY KEY(ssn);
ALTER TABLE EMPLOYEE ADD FOREIGN KEY(super_ssn) REFERENCES EMPLOYEE(ssn);
ALTER TABLE EMPLOYEE ADD FOREIGN KEY(dno) REFERENCES DEPARTMENT(dnumber);
ALTER TABLE DEPARTMENT ADD PRIMARY KEY(dnumber);
ALTER TABLE DEPARTMENT ADD FOREIGN KEY(mgr_ssn) REFERENCES EMPLOYEE(ssn);
ALTER TABLE DEPT_LOCATIONS ADD PRIMARY KEY(dnumber, dlocation);
ALTER TABLE DEPT_LOCATIONS ADD FOREIGN KEY(dnumber) REFERENCES DEPARTMENT(dnumber);
ALTER TABLE PROJECT ADD PRIMARY KEY(pnumber);
ALTER TABLE PROJECT ADD FOREIGN KEY(dnum) REFERENCES DEPARTMENT(dnumber);
ALTER TABLE WORKS_ON ADD PRIMARY KEY(essn, pno);
ALTER TABLE WORKS_ON ADD FOREIGN KEY(essn) REFERENCES EMPLOYEE(ssn);
ALTER TABLE WORKS_ON ADD FOREIGN KEY(pno) REFERENCES PROJECT(pnumber);
ALTER TABLE DEPENDENTS ADD PRIMARY KEY(essn, dependent_name);
ALTER TABLE DEPENDENTS ADD FOREIGN KEY(essn) REFERENCES EMPLOYEE(ssn);

Answer 1

Primary key column should be non null able. Table definition should have not null for all PKs.
CREATE TABLE EMPLOYEE (
fname varchar(100),
minit char(1),
lname varchar(100),
ssn char(9) not null,
bdate date,
addr varchar(100),
sex char(1),
salary int,
super_ssn char(9),
dno int
);
CREATE TABLE DEPARTMENT (
dname varchar(100),
dnumber int not null,
mgr_ssn char(9),
mgr_start_date date
);
CREATE TABLE DEPENDENTS (
essn char(9) not null,
dependent_name varchar(100) not null,
sex char(1),
bdate date,
relationship varchar(100)
);
CREATE TABLE DEPT_LOCATIONS (
dnumber int not null,
dlocation varchar(100) not null
);
CREATE TABLE PROJECT (
pname varchar(100),
pnumber int not null,
plocation varchar(100),
dnum int
);
CREATE TABLE WORKS_ON (
essn char(9) not null,
pno int not null,
hrs float
);
ALTER TABLE EMPLOYEE ADD PRIMARY KEY(ssn);
ALTER TABLE DEPARTMENT ADD PRIMARY KEY(dnumber);
ALTER TABLE EMPLOYEE ADD FOREIGN KEY(super_ssn) REFERENCES EMPLOYEE(ssn);
ALTER TABLE EMPLOYEE ADD FOREIGN KEY(dno) REFERENCES DEPARTMENT(dnumber);
ALTER TABLE DEPARTMENT ADD FOREIGN KEY(mgr_ssn) REFERENCES EMPLOYEE(ssn);
ALTER TABLE DEPT_LOCATIONS ADD PRIMARY KEY(dnumber, dlocation);
ALTER TABLE DEPT_LOCATIONS ADD FOREIGN KEY(dnumber) REFERENCES DEPARTMENT(dnumber);
ALTER TABLE PROJECT ADD PRIMARY KEY(pnumber);
ALTER TABLE PROJECT ADD FOREIGN KEY(dnum) REFERENCES DEPARTMENT(dnumber);
ALTER TABLE WORKS_ON ADD PRIMARY KEY(essn, pno);
ALTER TABLE WORKS_ON ADD FOREIGN KEY(essn) REFERENCES EMPLOYEE(ssn);
ALTER TABLE WORKS_ON ADD FOREIGN KEY(pno) REFERENCES PROJECT(pnumber);
ALTER TABLE DEPENDENTS ADD PRIMARY KEY(essn, dependent_name);
ALTER TABLE DEPENDENTS ADD FOREIGN KEY(essn) REFERENCES EMPLOYEE(ssn);