hi,
can anyone pla advice whether the contraits i have define for my oracle create tables statements is alright? or have i miss out any contraits?
contraits are based on this requirement:
- Only the courses on offer for a particular year/semester can be selected for that year/semester.
- No course could be selected more than once, no matter in the same semester or not.
- The number of units selected in any semester by a student cannot exceed 8 (including those year long courses, whose total number of units is split into the two semesters equally).
- A course has the same code, title, number of units and duration no matter when it is offered.
- Each semester-long course carries 2 units, and each year-long course carries 4 units.
- Only the existing courses in Courses dataset can be offered.
here is my create table statements:
CREATE TABLE Student(
StudentID VARCHAR2(8),
FamilyName VARCHAR2 (50) NOT NULL,
GivenName VARCHAR2 (50) NOT NULL,
StudentPwd VARCHAR2(8) NOT NULL,
CONSTRAINT pk_Student PRIMARY KEY (StudentID));
CREATE TABLE Course(
CourseCode VARCHAR2(8),
CourseTitle VARCHAR2 (100) NOT NULL,
CONSTRAINT pk_Course PRIMARY KEY (CourseCode));
CREATE TABLE StudentEnrolment(
CourseCode VARCHAR2(8),
StudentID VARCHAR2(8),
EnrolledYear INTEGER NOT NULL,
EnrolledSem INTEGER NOT NULL,
CONSTRAINT pk_StudentEnrolment PRIMARY KEY (CourseCode, StudentID, EnrolledYear, EnrolledSem),
CONSTRAINT fk_StudentEnrolment1 FOREIGN KEY (CourseCode)
REFERENCES Course (CourseCode),
CONSTRAINT fk_Student_Enrolment2 FOREIGN KEY (StudentNo)
REFERENCES Student (StudentNo));
CREATE TABLE CourseOffering(
CourseCode VARCHAR2(8),
Year INTEGER NOT NULL,
Sem VARCHAR2(6) NOT NULL,
Title VARCHAR2(100) NOT NULL,
Duration VARCHAR2(4),
UnitNum VARCHAR2(1) NOT NULL,
CONSTRAINT pk_CourseOffering PRIMARY KEY (CourseCode, year, sem),
CONSTRAINT fk_CourseOffering FOREIGN KEY (CourseCode)
REFERENCES Course (CourseCode));
thank you.
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I object:
*) original question has been answered
*) second question (any references?) was already answered by vchavan (use the book by Baryoss on Oracle)
Anyway, q seems to be homework, thus no complete solution should be given (EE rules)...
Finally, no explanation of why the q should be deleted!
Best Regards
Business Accounts
Answer for Membership
by: angelIIIPosted on 2003-05-20 at 01:32:36ID: 8549141
most of the constraints are NOT implemented or incorrect:
- Only the courses on offer for a particular year/semester can be selected for that year/semester.
This is not implemented at all. If you disagree, show where you think you implemented it (CourseEnrolment -> CourseOffering)
- No course could be selected more than once, no matter in the same semester or not.
This means 1 student cannot choose 1 course more than once, this is also not implemented (CourseEnrolment -> CourseOffering)
- The number of units selected in any semester by a student cannot exceed 8 (including those year long courses, whose total number of units is split into the two semesters equally).
This is not implemented at all (is the most difficult one)
- A course has the same code, title, number of units and duration no matter when it is offered.
Check Course and Courseoffering table, some columns are in the wrong table.
- Each semester-long course carries 2 units, and each year-long course carries 4 units.
This means you need a check on the data (UnitNum) which can have limited values only... (Not implemented)
- Only the existing courses in Courses dataset can be offered.
OK
You have some more work to do...