on sql Foreign key - database

Question

Can someone help me in SQL I'm using Oracle SQL*plus
Create the following tables.
Table Student:
stdNo CHAR(5) This is the Primary Key
lastname VARCHAR(25) Must be Not Null
givennames VARCHAR(50) Must be Not Null
Dept CHAR(4)
Table Course:
courseID CHAR(8) This is the Primary Key
courseTitle VARCHAR(50) Must be Unique and Not Null
Cost DECIMAL(6,2) Ensure Cost is greater or equal to zero
Credits INT Ensure that Credits are between 0 and 200. Also the default value is 2
Table Semester:
semesterID CHAR(5) This is the Primary Key
semesterCode INT Ensure that semesterCode is Between 1 and 4
Year INT Ensure that year is Between 2000 and 9999
Table Register:
stdNo CHAR(5) Foreign Key referenced to stdNo in Student table, On update cascade On delete cascade
courseID CHAR(8) Foreign Key referenced to courseID in Course table, On update cascade On delete cascade
semesterID CHAR(5) Foreign Key referenced to semesterID in Semester table, On update cascade On delete cascade
Grade CHAR(2)
Mark DECIMAL(4,2) Mark should be between 0.00 and 100.00
Primary Key (stdNo, courseID, semesterID)
Here in SQL (I'm using Oracle SQL*plus) .. table STD , SEMESTER works with me, but table COURSE I did not know how to put default value is 2 and table REGISTER dose not work with me at all :(
CREATE TABLE STD
(
STDNO CHAR(5) PRIMARY KEY,
LASTNAME VARCHAR(25) NOT NULL,
GIVENNAME VARCHAR(50) NOT NULL,
DEPT CHAR(4)
);
CREATE TABLE SEMESTER
(
SEMESTERID CHAR(5) PRIMARY KEY,
SEMESTERCODE INT CHECK(SEMESTERCODE BETWEEN 1 AND 4),
YEARS INT CHECK(YEARS BETWEEN 2000 AND 9999)
);
CREATE TABLE COURSE
(
COURSEID CHAR(8) PRIMARY KEY,
COURSETITLE VARCHAR(50) NOT NULL UNIQUE,
COST DECIMAL(6,2) CHECK(COST >= 0),
CREDITS INT CHECK(CREDITS BETWEEN 0 AND 200)
);
CREATE TABLE REGISTER
(
STDNO CHAR(5)
FOREIGN KEY REFERENCES STD(STDNO)
ON UPDATE CASCADE ON DELETE CASCADE,
COURSEID CHAR(5)
FOREIGN KEY REFERENCES COURSE(COURSEID)
ON UPDATE CASCADE ON DELETE CASCADE,
SEMESTERID CHAR(5)
FOREIGN KEY REFERENCES SEMESTER(SEMESTERID)
ON UPDATE CASCADE ON DELETE CASCADE,
GRADE CHAR(2),
MARK DECIMAL(4,2) CHECK(MARK BETWEEN 0.00 AND 100.0),
PRIMARYKEY(STDNO,COURSEID,SEMESTERID)
);

Answer 1

Please find below the solution.
COURSE - please use the below script to have a default value for CREDITS column
CREATE TABLE COURSE
(
COURSEID CHAR(8) PRIMARY KEY,
COURSETITLE VARCHAR(50) NOT NULL UNIQUE,
COST DECIMAL(6,2) CHECK(COST >= 0),
CREDITS INT DEFAULT 2 CHECK(CREDITS BETWEEN 0 AND 200)
);
REGISTER - Oracle Does not allow a Foreign Key Constraint with "ON UPDATE CASCADE". So you will have to use triggers for the same. Find below the scripts that you could make use of,
CREATE TABLE REGISTER
(
STDNO CHAR(5),
COURSEID CHAR(8), -- UPDATED THE DATATYPE TO SAME AS MASTER TABLE
SEMESTERID CHAR(5),
GRADE CHAR(2),
MARK DECIMAL(4,2) CHECK(MARK BETWEEN 0.00 AND 100.0),
CONSTRAINT register_pk PRIMARY KEY(STDNO,COURSEID,SEMESTERID),
CONSTRAINT register_fk1 FOREIGN KEY (STDNO) REFERENCES STD(STDNO)
ON DELETE CASCADE,
CONSTRAINT register_fk2 FOREIGN KEY (COURSEID) REFERENCES COURSE(COURSEID)
ON DELETE CASCADE,
CONSTRAINT register_fk3 FOREIGN KEY (SEMESTERID) REFERENCES SEMESTER(SEMESTERID)
ON DELETE CASCADE
);
CREATE OR REPLACE TRIGGER cascade_stdno_update
AFTER UPDATE OF stdno ON std
FOR EACH ROW
BEGIN
UPDATE REGISTER
SET stdno = :NEW.stdno
WHERE stdno = :OLD.stdno;
END;
/
CREATE OR REPLACE TRIGGER cascade_courseid_update
AFTER UPDATE OF courseid ON course
FOR EACH ROW
BEGIN
UPDATE REGISTER
SET courseid = :NEW.courseid
WHERE courseid = :OLD.courseid;
END;
/
CREATE OR REPLACE TRIGGER cascade_semesterid_update
AFTER UPDATE OF semesterid ON semester
FOR EACH ROW
BEGIN
UPDATE REGISTER
SET semesterid = :NEW.semesterid
WHERE semesterid = :OLD.semesterid;
END;
/