Triggers working correctly, but raise application error causing some errors with insert statements - sql

Question

I have my code shown below. Everything is working correctly but when my insert statements violate the trigger it throws errors because of my raise_application_error.
--Drop tables in case they were created previously
DROP TABLE enrollment Purge;
DROP TABLE offering Purge;
DROP TABLE faculty Purge;
DROP TABLE course Purge;
DROP TABLE student Purge;
--Create student table
CREATE TABLE student(StdID number(3) constraint student_StdID_PK primary key,
StdFN varchar2(10),
StdLN varchar2(15),
StdCity varchar2(15),
StdState char(2),
StdZip number(5),
StdMajor varchar2(4),
StdClass char(2),
StdGPA number(2,1),
StdBalance NUMBER (12,2));
--create a table for courses and their descriptions
CREATE TABLE course(CourseNo varchar2(8) constraint course_courseNo_PK primary key,
CrsDesc varchar2(40),
CrsCredits number(1));
--create faculty table
CREATE TABLE Faculty(FacID number(4) constraint faculty_FacID_PK primary key,
FacFN varchar2(10),
FacLN varchar2(15),
FacDept varchar2(4),
FacRank varchar2(4),
FacHireDate date,
FacSalary number(6),
FacSupervisor number(4));
--create table for offered courses
CREATE TABLE Offering(OfferNo number(4) constraint offering_OfferNo_PK primary key,
CourseNo varchar(8)constraint offering_crs_no references course(courseno),
OffTerm varchar2(6),
OffYear number(4),
OffLoca varchar(6),
OffTime varchar(8),
OffDay varchar(5),
FacSSN number(4)constraint offering_fac_FK references faculty(facID));
--create table for student enrollment
CREATE TABLE enrollment(StdID number(3),
OfferNo number(4),
EnrGrade char(2),
constraint enrollment_PK primary key (StdID,OfferNo),
constraint enrollment_std_ID foreign key(StdID) references student(stdID),
constraint enrollment_class_ID foreign key(offerno) references offering(offerno));
CREATE OR REPLACE TRIGGER UNPAID_BALANCE
BEFORE INSERT ON STUDENT
FOR EACH ROW
DECLARE
BAL NUMBER;
BEGIN
BAL := :NEW.STDBALANCE;
IF BAL > 500
THEN
RAISE_APPLICATION_ERROR(-20001, 'Your balance is too high to register. Please pay to continue.');
END IF;
END;
/
CREATE OR REPLACE TRIGGER ENROLL_MAX
BEFORE INSERT ON ENROLLMENT
FOR EACH ROW
DECLARE
NOFSTUDENTS BINARY_INTEGER;
BEGIN
SELECT COUNT(*) INTO NOFSTUDENTS
FROM ENROLLMENT
WHERE OFFERNO = :NEW.OFFERNO AND ENRGRADE IS NULL;
DBMS_OUTPUT.PUT_LINE(NOFSTUDENTS);
IF (NOFSTUDENTS + 1) > 2
THEN
RAISE_APPLICATION_ERROR(-20003, 'EXCEED MAX NO OF STUDENTS ALLOWED');
END IF;
END;
/
--populate student table
INSERT INTO student values(101,'Joe','Smith','Eau Clare','WI',18121,'IS','FR',3.8,225.25);
INSERT INTO student values(102, 'Rob','King', 'Melrose', 'MN', 56352, 'IS','JR',3.2,120.98);
INSERT INTO student values(103, 'Dan','Robinson', 'Sartell', 'MN', 98042, 'IS','JR',3.6, 36);
INSERT INTO student values(104,'Sue','Williams','St.Cloud','MN',56301,'ACCT','SR',3.2,2386.55);
INSERT INTO student values(105,'Don','Robinson','St.Paul','MN',55103,'MKTG','SR',3.4, 306);
--populate course table
INSERT INTO Course values('CSCI 200','Elements of Computing',3);
INSERT INTO Course values('IS 250','Application of Program Dev. I',3);
INSERT INTO Course values('IS 251','Application of Program Dev. II',3);
INSERT INTO Course values('IS 454', 'Data Mining for Decision Support',3);
INSERT INTO Course values('IS 356','Systems Analysis and Design I',3);
INSERT INTO Course values('IS 460', 'Project Management',3);
INSERT INTO Course Values('ACCT 291','Accounting Principles II',3);
INSERT INTO Course values('IS 443','Database Design',3);
--populate faculty table
INSERT INTO faculty values(9001,'Leonard','Vince','IS','ASST','12-Apr-1997',67000,9003);
INSERT INTO faculty values(9002,'Victor','Strong','CSCI','ASSO','8-Aug-1999',70000,9003);
INSERT INTO faculty values(9003,'Nicki','Colan','IS','PROF','20-Aug-1981',75000,9010);
INSERT INTO faculty values(9004,'Fred','Wells','ACCT','ASST','28-Aug-1996',60000,9010);
INSERT INTO faculty values(9010,'Chris','Macon','ACCT','ASST','4-Aug-1980',75000,Null);
--populate offering table
INSERT INTO offering values(2201,'CSCI 200','Spring',2017,'ECC135','10:30AM','MWF',9002);
INSERT INTO offering values(2202,'CSCI 200','Spring',2017,'ECC135','8:00AM','MWF',9002);
INSERT INTO offering values(1102,'ACCT 291','Spring',2017,'CH 14A','2:00AM','MWF',9004);
INSERT INTO offering values(2203,'IS 356','Fall',2017,'CH494','3:30AM','TTH',9001);
INSERT INTO offering values(2204,'IS 251','Fall',2017,'CH494','12:30AM','TTH',9003);
INSERT INTO offering values(1101,'ACCT 291','Fall',2017,'CH350','12:30AM','TTH',9010);
INSERT INTO offering values(2205,'IS 443','Fall',2017,'CH494','9:30AM','MWF',9003);
--populate enrollment table
INSERT INTO enrollment values(101,2201,'A');
INSERT INTO enrollment values(102,2202,'B');
INSERT INTO enrollment values(102,2203,null);
INSERT INTO enrollment values(103,2203,null);
INSERT INTO enrollment values(103,2201,'C');
INSERT INTO enrollment values(103,1101,null);
INSERT INTO enrollment values(104,2202,'A');
INSERT INTO enrollment values(101,2203,null);
INSERT INTO enrollment values(101,1101,null);
INSERT INTO enrollment values(101,2205,null);
INSERT INTO enrollment values(102,2205,null);
INSERT INTO enrollment values(104,2205,null);
Is there a way I can make this look cleaner/better in the script output section because one specific case is this error message that pops up because of the raise application error.
Error starting at line : 129 in command -
INSERT INTO enrollment values(104,2202,'A')
Error report -
ORA-02291: integrity constraint (ADMIN_BF.ENROLLMENT_STD_ID) violated - parent key not found

Answer 1

The error that you are facing is clear enough. There is not student 104 in the table, so you cannot create a dependent record in enrollment. This error is not related to your triggers, but to your data.
Now let's look at the insert statement for that particular user:
INSERT INTO student values(104,'Sue','Williams','St.Cloud','MN',56301,'ACCT','SR',3.2,2386.55);
You are attempting to input a balance of 2386.55. But your trigger UNPAID_BALANCE prevents balances that are above 500, so that insert raises application error "Your balance is too high to register", which is the root cause of the problem. You need to fix that insert.
Side note: there is another problem lurking in the last series of inserts into enrollments. Trigger ENROLL_MAX allows only two students per OFFERNO, but you are attempting to assign three students to offer 2203, and three as well to offer 2205. This will raise application error "EXCEED MAX NO OF STUDENTS ALLOWED".