Relational Algebra - Selection, Projection, Joins etc

The relational algebra defines a set of operations on relations, paralleling the usual algebraic operations such as addition, subtraction etc which operate on numbers.The relational algebra operations take one or two relations (tables) as input and return a relation as output. This post we discuss the following relational operations:

1. Selection (σ)
2. Projection (π)
3. Cartesian product
4. Joins

Selection Operation (σ)