Suppose that we have the following requirements for a university database that i

Question

Suppose that we have the following requirements for a university database that is used to keep of students transcripts: The university keeps track of each student's name (Sname), student number (Snum), social security number (Ssn), current address (Sc_add) and phone (So_phone), permanent address (Sp_addr) and phone (Sp_phone), birth date (Bdate), sex (Sex), class(Class) ('freshman, 'graduate'), major department (Major_code), minor department (Minor_code) (if any), and degree program (Prog) Both Son and student number have unique values for each student. Each department is described by a name (Dname), department code (Dcode), office number (Doffice), office phone (Dphone), and college (Dcollege). Both name and code have unique values for each department. Each course has a course name (Cname), description (Cdesc), course number (Cnum), number of semester hours (Credit), level (Level), and offering department (Cdept). The course number is unique for each course. Each section has an instructor (In ), semester (Semester), year (year), course (Sec_course), and section number (Sec_num),The section number distinguishes different sections of the same course that are taught during the same semester/year; its value are 1, 2, 3, . up to the total number of sections taught during each semester. A grade record refers to a student (Ssn), a particular section, and a grade (Grade). Design a relational database schema for this database application. First show all the functional dependencies that should hold among the attributes. Then design relation schemas for the database that are each in 3NF or BCNF. Specify the key attributes of each relation. Note any unspecified requirements, and make appropriate assumptions to render the specification complete. Prove or disprove the following inference rules for functional dependencies. A proof can be made either by a proof argument or by using inference rules IR1 through IR3. A disproof should be performed by demonstrating a relation instance that satisfies the conditions and functional dependencies in the left-hand side of the inference rule but does not satisfy the dependencies in

Explanation / Answer

by Ebenezer January 22, 2009 "Dear... From the university database take the Functional dependencieshold on the attributes: Now apply the inferencerules IR1 to IR3, then FD1 andFD2 are refer to student attributes. And we can define arelation STUDENT and choose either SSSN or SNUM as its primary key.Similarly, FD3 and FD4 refer to department attributes, with eitherDEPTNAME or DEPTCODE as primary key. FD5 defines COURSEattributes, and FD6 SECTION attributes. FD7 defines GRADESattributes. So, We can create one relation for each of STUDENT,DEPARTMENT, COURSE, SECTION, and GRADES as shown below, withrespect to the primary keys. Here COURSE, SECTION, and GRADESrelations are in 3NF and BCNF if no other dependencies exist. TheSTUDENT and DEPARTMENT relations are in 3NF and BCNF, since bothrelations have secondary keys. Foreign keys will be as follows: STUDENT.MAJOR ->DEPARTMENT.DEPTCODE STUDENT.MINOR ->DEPARTMENT.DEPTCODE COURSE.CDEPT ->DEPARTMENT.DEPTCODE SECTION.SECCOURSE ->COURSE.CNUM GRADES.(SECCOURSE, SEMESTER, YEAR,SECNUM) -> SECTION.(SECCOURSE, SEMESTER, YEAR, SECNUM) GRADES.SNUM -> STUDENT.SNUM I hope it is useful to you. Further clarification, beon tough with CRA+MSTER ." -Ebenezer January 22, 2009

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