SQL: ORA-02291: integrity constraint violated - parent key not found - oracle

Question

I am creating this code SQL code and I keep getting the same error from every line of the insert statements after the errors begin here statement. the error is, ORA-02291: integrity constraint violated - parent key not found. I think it has something to do with the employee section constraint EMPSUPERVRFK but, that is the only constraint that the error message would lead to.
-- keep these two commands at the top of every sql file
set echo on
set linesize 120
delete from Employee;
commit;
-- insert only managers first with their dno is null
INSERT INTO Employee VALUES
('James','E','Borg',888665555,'10-NOV-1937','450 Stone, Houston, TX','M',55000,null,null);
INSERT INTO Employee VALUES
('Franklin','T','Wong',333445555, to_date('1955-12-08', 'YYYY-MM-DD'), '638 Voss, Houston, TX','M',40000,888665555,null);
INSERT INTO Employee VALUES
('Jennifer','J','Zelaya',987654321,'20-JUN-1941','291 Berry, Bellaire, TX','F',43000,888665555,null);
delete from Department;
commit;
insert into Department values ('Research',5,333445555,'22-MAY-1988');
insert into Department values ('Headquarters',1,888665555,'19-JUN-1981');
insert into Department values ('Administration',1,888665555,'01-JAN-1995');
-- now, update employee.dno for managers
UPDATE Employee SET dno = 1 WHERE ssn = 888665555;
UPDATE Employee SET dno = 5 WHERE ssn = 333445555;
-- need to update the rest of managers
-- insert the rest of non-manager employees, supervisors first
--errors begin here
delete from Employee;
commit;
INSERT INTO Employee VALUES ('John','B','Smith',123456789,'09-JAN-1965','731 Fondren, Houston, TX','M',30000,333445555,5);
insert into Employee values ('Alica','J','Zelya',999887777,'19-JAN-1968','3321 Castle, Spring, TX','F',25000,987654321,4);
insert into Employee values ('Ramesh','K','Narayan',666884444,'15-SEP-1962', '975 Fire Oak, Humnle, TX','M',38000,333445555,5);
insert into Employee values ('Joyce','A','English',453453453,'31-JUL-1972','5631 Rice, Houston, TX','F',25000,333445555,5);
insert into Employee values ('Ahmad','V','Jabbar',987987987,'29-MAR-1969','980 Dallas, Houston, TC','M',25000,987654321,4);
--Project
delete from PROJECT;
commit;
insert into PROJECT values ('ProductY',2,'Sugarland',5);
insert into PROJECT values ('ProductZ',3,'Houston',5);
insert into PROJECT values ('Computerication',10,'Stafford',4);
insert into PROJECT values ('Reorganization',20,'Houston',1);
insert into PROJECT values ('Newbenefits',30,'Stafford',4);
--dept_Locations
delete from DEPT_LOCATIONS;
commit;
insert into DEPT_LOCATIONS values (1, 'Houston');
insert into DEPT_LOCATIONS values (4,'Stafford');
insert into DEPT_LOCATIONS values (5,'Bellaire');
insert into DEPT_LOCATIONS values (5,'Sugarland');
insert into DEPT_LOCATIONS values (5,'Houston');
--works_on 16
delete from WORKS_ON;
commit;
insert into WORKS_ON values (123456789,1,32.5);
insert into WORKS_ON values (123456789,2,7.5);
insert into WORKS_ON values (666884444,3,40.0);
insert into WORKS_ON values (453453453,1,20.0);
insert into WORKS_ON values (453453453,2,20.0);
insert into WORKS_ON values (333445555,2,10.0);
insert into WORKS_ON values (333445555,3,10.0);
insert into WORKS_ON values (333445555,10,10.0);
insert into WORKS_ON values (333445555,20,10.0);
insert into WORKS_ON values (999887777,30,30.0);
insert into WORKS_ON values (999887777,10,10.0);
insert into WORKS_ON values (987987987,10,35.0);
insert into WORKS_ON values (987987987,30,5.0);
insert into WORKS_ON values (987654321,30,20.0);
insert into WORKS_ON values (987654321,20,15.0);
insert into WORKS_ON values (888665555,20,null);
--dependent 7
delete from DEPENDENT;
commit;
insert into DEPENDENT values (333445555,'Alice','F','05-APR-1986','Daughter');
insert into DEPENDENT values (333445555,'Theodore','M','25-OCT-1983','Son');
insert into DEPENDENT values (333445555,'Joy','F', '03-MAY-1958','Spouse');
insert into DEPENDENT values (987654321,'Abner','M', '28-FEB-1942','Spouse');
insert into DEPENDENT values (123456789,'Michael','M','04-JAN-1988','Son');
insert into DEPENDENT values (123456789,'Alice','F','30-DEC-1988','Daughter');
insert into DEPENDENT values (123456789,'Elizabeth','F', '05-MAY-1967','Spouse');
-----------------------------------------------------------------------------------
set echo on
set linesize 120
drop table Employee cascade constraints;
commit;
create table Employee
(
fname varchar2(15),
minit varchar2(1), -- can be char
lname varchar2(15),
ssn number,
bdate date,
address varchar2(50),
sex varchar2(1) CHECK(Sex = 'M' or Sex = 'F'),
salary number CHECK(20000 <= salary AND 100000 >= salary),
superssn number,
dno number DEFAULT 0,
constraint EMPPK
primary key(ssn),
constraint EMPSUPERVRFK
foreign key(superssn) references Employee(ssn)
ON DELETE SET NULL
);
drop table Department cascade constraints;
commit;
create table Department
(
dname varchar2(15),-- NOT NULL,
dnumber number,
mgrssn number,
mgrstartdate date,
constraint DEPTPK
primary key(dnumber),
constraint DEPTMGRFK
foreign key(mgrssn) references Employee(ssn)
ON DELETE SET NULL
);
alter table Employee add
constraint EMPDEPTFK foreign key(dno) references Department(dnumber)
ON DELETE SET NULL;
drop table DEPT_LOCATIONS;
create table DEPT_LOCATIONS
(
Dnumber number,
Dlocation varchar2(15),
constraint PK_DnoDloc primary key(Dnumber,Dlocation)
);
COMMIT;
drop table PROJECT;
create table PROJECT
(
Pname varchar2(15),
Ponumber number primary key,
Plocation varchar2 (15),
Dnum number,
foreign key (Dnum) references Department(dnumber)
);
Commit;
drop table DEPENDENT;
create table DEPENDENT
(
Essn number,
Dependent_name varchar2(15),
Sex Char,
Bdate Date,
Relationship varchar2(15),
foreign key(Essn) references Employee(ssn) --
ON DELETE SET NULL,
constraint PK_essn
primary key(Essn,Dependent_name)
);
COMMIT;
drop table WORKS_ON;
create table WORKS_ON
(
Essn number,
Pno number,
Hours number,
foreign key(Essn) references Employee(ssn)--
ON DELETE SET NULL,
foreign key(Pno) references PROJECT(Ponumber)
ON DELETE SET NULL,
constraint PK_SSN
primary key(Essn, Pno)
);
commit;
----------------------------------------------------------------
-- keep these two commands at the top of every sql file
set echo on
set linesize 120
-- test queries, not to be submitted
select count(*) from employee;
select count(*) as DEPT_COUNT from department;
-- comment out the above queries for your homework
-- a the first name, last name of employees who work in department 5.
select fname, lname from employee where dno = 5;
-- b the first name, last name of every employee and name of his/her department
select E.fname as FIRST_NAME, E.lname LAST_NAME, D.dname DEPARTMENT_NAME
from employee E, department D
where E.dno = D.dnumber;
--c The first name, last name of employees who works at the 'Research' department
select e.fname , e.lname , Dname
from employee e inner join department d on e.dno=d.dname
where d.name ='Research';
--d. The first name, last name of employee who is the manager of the 'Research' department
select e.fname , e.lname , Dname
from employee e inner join department d on e.dno=d.dname
where d.name ='Research' and e.super_ssn=d.mgr_ssn;
--e. The first name, last name of employees who works on the 'Computerization' project.
select e.fname,e.lname
from employee e inner join department d on e.dno=d.dnumber inner join project p on d.dnumber=p.dnum
where p.pname="Computerization";

Answer 1

this happens because you are inserting values to table that depends on other table that is still empty, you should insert on that table first before this one
for example, suppose you have employee table, and department table, in which every employee must be assigned to a department, so when you input employee Bob to department IT, it would result in error, since there is no IT yet in department table. so you need to input IT on department table, then you can input Bob to employee table
or, you can disable integrity check when importing sql, but this setting is different for each DB engine, so I can't give you an example