Normalisation

Question 1. Normalisation (6 points).

Consider the following relational database schema about employees from departments working on projects:

Employee(empNo, givename, surname, DOB, gender, deptNo, dept_name)
Department(deptNo, dept_name, location, manager)
WorkOn(empNo, projNo, proj_name, deptNo, hours)

Some notes on the semantics of attributes are as follows:
⦁ Each employee has a unique employee number (empNo) and work for a department.
⦁ Each department has a unique department number (deptNo), a manager and possibly several locations.
⦁ Each project has a unique project number (projNo). A project also has an “owning” department.
⦁ Employees work on projects for some hours.

FDs based on business rules are given as follows:

⦁ empNo givename, surname, DOB, deptNo, dept_name
⦁ deptNo dept_name, manager
⦁ projNo proj_name, deptNo, dept_name
⦁ empNo, projNo proj_name, deptNo, hours

Answer questions below:
⦁ (3 points) Identify and annotate the primary key (underline) and any foreign keys (asterisk) for each given relation. Give the highest normal form for each relation. Explain your answer using the given FDs. Note that relations must be written in the form as shown in the examples below:

Student(sno, name, address)
Course(cno, title)
Take(sno*, cno*, grade)

1.2 (3 points) Decompose any given relation not in BCNF or 3NF into relations in BCNF or 3NF. Your decomposition must keep all functional dependencies and must be lossless. Show your working for the decomposition. For each resultant relation, explain if it is in BCNF or 3NF and annotate the primary key (underline) and any foreign keys (asterisk).

 

 

Question 2. The ER Model (8 points).
The XB Records management has decided to build a database storing information about artists who perform for their albums. The company has hired you to design the database. Description of the database is as follows.

⦁ Each artist has a unique ID, a name, and an address.
⦁ A band has a name, year established and place of origin. A band has several artists. An artist usually is a member of only one band at a time.
⦁ Each song has an ID and a title.
⦁ Genres of songs are described by a unique name, some description. For example, “rock” is a genre with the description “rock music originated as ‘rock and roll’ in the United States”. A genre may have many songs.
⦁ Each album recorded on the XB label has a title, a release date, a format (such as CD, MP3), and a unique album number. Each album has many tracks on it (up to 20 usually), and they are numbered sequentially. Each track of an album usually corresponds to a song.
⦁ An album may be by an artist or a band (but not both).
⦁ A song may appear on several albums. A song has one or more genres, and a genre may have many songs.

Examples for queries on the database:
⦁ Look up the details of artists, bands, songs and albums.
⦁ List the songs and their track number for the album “Thriller” (title).
⦁ Give the number of songs for each genre.
⦁ Find the albums by an artist named “Bob Janes”.
⦁ Give the name of the band for the album “The Last Waltz”.
⦁ How many albums have the song “Almost is Never Enough”?

According to the data requirements and query requirements above, give the ER diagram for the database using the UML class diagram symbols (as used in the lecture notes and tutorials), making appropriate assumptions where necessary. You must represent entity types, relationships and their attributes, and all applicable constraints in your diagram. Explain any constraints that are not expressed in the diagram. Note that your ER diagram would be mapped to a relational database schema and implemented as tables using a DBMS. It may be helpful that you do this mapping and see if the queries can be answered using the mapped relations to help you refine the ER diagram.

Question 3. ER to Relational Schema Mapping (6 points).
Consider the ER diagram for a Software Testing database below using UML class diagram symbols. Map the diagram to a relational database schema. Indicate the primary key (underline) and any foreign keys (asterisk) for each relation. Note that a relational database schema comprises a set of relation schemas written in the form as shown in the examples below:

Student(sno, name, address)
Course(cno, title)
Take(sno*, cno*, grade)

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