Relational Algebra

Question 1

What is relational algebra?

Answer 1

A form of algebra that has relations in place of operators.

Question 2

How does relational algebra enable database querying?

Answer 2

SQL queries are converted to relational algebra via the Relational Data Management System.

Question 3

What are the 3 main types of relational algebra operations?

Answer 3

Unary, Set, Binary.

Question 4

What are the 3 Unary operations?

Answer 4

SELECT : New relation based on the tuples that satisfy the select condition.
PROJECTION : New relation of certain attributes.
RENAME : Rename a relation as well as specified attributes.

Question 5

What are the 3 types of Set operations?

Answer 5

Union, Intersection, Difference, Cartesian Product.

Question 6

What are the 3 Joins in the Binary operations?

Answer 6

Theta Join : New relation containing all tuples of a cartesian product that satisfy the join condition.
Equijoin : Create a relation from R1 and R2 where the equality comparotor between the relations is satisfied. For example Student.age == Teacher.age
Natural Join : An equijoin of R1 and R2 over all common attributes.