Which combinations of attributes have to be unique for each individual SECTION entity in the UNIVERSITY database shown in Figure 3.20 to enforce each of the following miniworld constraints:
a. During a particular semester and year, only one section can use a particular classroom at a particular DaysTime value.
b. During a particular semester and year, an instructor can teach only one section at a particular DaysTime value.
c. During a particular semester and year, the section numbers for sections offered for the same course must all be different.

 

COffice Rank IOffice CName CPhone Id IName IPhone COLLEGE DEAN INSTRUCTOR (1,1) (0,1) (0,N) CStartDate (0,1) (0,N) CHAIR (1,1). ADMINS MName FName (1,1), (1,1) EMPLOYS LName DName Sld SName (0,N) DOB Addr DCode DEPT HAS STUDENT Phone DOffice (0,N) (0,1) Major DPhone (0,N) (0,N) Grade OFFERS TAKES TEACHES (1,1) (5,N) (1,1) Secld CCode COURSE SECS SECTION SecNo Credits (0,N) (1,1) COName Days Time Sem CDesc Level Year CRoom Bldg RoomNo Figure 3.20 An ER diagram for a UNIVERSITY database schema.