Introduction to Databases Assignment -

Learning Outcome(s):

• Define the relational model.
• Identify the appropriate primary key and foreign key in a given relation.
• Describe different types of relational model keys and their use in databases.
• Define the operations of the relational algebra.

Question One - Consider the following three relations:

For each of the following relational expressions, compute the result on the above relations and submit only the final answer. For example, for query: πB,D(S), the result should be entered as: {(a, x), (b, y), (b, x), (c, y)}.

a. π_A,D(R×S)

b. π_A,D(R∞S)

c. π_E(T)-π_E(S∞T)

a. πA,D(R×S)=?**(1, x), (1, y), (2, x), (2, y), (3, x), (3, y)**

b. πA,D(R∞S)=?**(1, x), (1, y), (2, x), (2, y), (3, y)**

c. πE(T)-πE(S∞T) =** (3) **

Question Two -  Consider the Bank database:

a. What are the appropriate primary keys in each relation?

b. Given your choice of primary keys, identify appropriate foreign keys.

Question Three - Consider the relational database of instructor:

a. Identify at least four possible super keys?

b. Identify at least three possible candidate keys?

Question Four - Employee (Id, emp_name, age, occupation_Id, city_Id)

Occupation (occupation_id, occup_name)

City (city_id, city_name)

Consider the above relational database. Give an expression in the relational algebra to express each of the following queries:

a. Find the names and ages of all employees who work in "New York".

b. Find the names and cities of all employees who work as "Software Engineer".