Foreign key errors in sql plus

Question

Hello, im pretty new to sql and i am stuck on a project in my database management class and i was wondering if anyone can help us out. I don't know if it would be easier to send what i've done or just post the error so if anyone could help it will be appreciated.
This is one part of the sql
CREATE TABLE PREREQUISITE_T
     (COURSECODE                VARCHAR2(10)NOT NULL,
     PREREQUISITECODE          VARCHAR2(20),
PRIMARY KEY (COURSECODE),
PRIMARY KEY (PREREQUISITECODE),
FOREIGN KEY (COURSECODE) REFERENCES COURSE_T(COURSECODE),
FOREIGN KEY (PREREQUISITECODE));
INSERT INTO PREREQUISITE_T VALUES ('23131', '3213');
INSERT INTO PREREQUISITE_T VALUES ('23541', '4213');
INSERT INTO PREREQUISITE_T VALUES ('23251', '3413');
INSERT INTO PREREQUISITE_T VALUES ('56131', '3513');
INSERT INTO PREREQUISITE_T VALUES ('75431', '3613');
INSERT INTO PREREQUISITE_T VALUES ('45631', '3813');
INSERT INTO PREREQUISITE_T VALUES ('65461', '3913');
INSERT INTO PREREQUISITE_T VALUES ('45351', '5413');
the error i get is
ERROR at line 1:
ORA-02298: cannot validate (STUDENT.SYS_C003016) - parent keys not found
It works fine without the primary keys but when i put in foreign keys it is all messed up. If there a a tutorial or anyone could take a look at the rest of the code i can send it out. Any help is appreciated.

Answer 1

probably u had given the column value not exists in the reference table.
see the example
create table tst(x number ,y number);
alter table tst add constraints pk_x primary key(x);
create table tst1(x number, y number);
alter table tst1 add constraints fk_x foreign key(x) references tst(x);
SQL> insert into tst values(&x,&y);
Enter value for x: 1
Enter value for y: 2
old 1: insert into tst values(&x,&y)
new 1: insert into tst values(1,2)
1 row created.
SQL> /
Enter value for x: 2
Enter value for y: 3
old 1: insert into tst values(&x,&y)
new 1: insert into tst values(2,3)
1 row created.
SQL> commit;
Commit complete.
SQL> insert into tst1 values(&x,&y);
Enter value for x: 2
Enter value for y: 1
old 1: insert into tst1 values(&x,&y)
new 1: insert into tst1 values(2,1)
1 row created.
SQL> /
Enter value for x: 5
Enter value for y: 6
old 1: insert into tst1 values(&x,&y)
new 1: insert into tst1 values(5,6)
insert into tst1 values(5,6)
ERROR at line 1:
ORA-02291: integrity constraint (SHFLDEV.FK_X) violated - parent key not found