ITPEC FE Morning October 2018 Question 29

Relational Algebra Operations — identify operations to derive a result relation from a join.

After joining relations X and Y on FacultyCode, the result has columns: StudentNumber, Name, FacultyCode, FacultyName with 6 rows.

To obtain relation Z (FacultyName, StudentNumber, Name with only "Information" rows):

• •Selection — filter rows where FacultyName = 'Information' (2 rows remain)
• •Projection — remove FacultyCode, keeping only FacultyName, StudentNumber, Name

Why not others:
- (b) Projection and union — union combines two relations; not needed here
- (c) Selection — selection alone keeps all columns; Z has fewer columns than the join result
- (d) Selection and union — union is not applicable in this scenario

Key rule: Selection = row filtering (like SQL WHERE). Projection = column selection (like SQL SELECT col1, col2).

AI-generated — may contain errors