Relational Algebra is procedural query languages, which takes Relation as input and generate relation as output. Relational algebra mainly provides theoretical foundation for relational databases and SQL.

**Selection (σ)**

Selection is used to select required tuples of the relations.

**Projection (π) **:Projection is used to project required column data from a relation.

** Union (U)**

Union operation in relational algebra is same as union operation in set theory, only constraint is for union of two relations both relations must have same set of Attributes

**Set Difference (-)**

Set Difference in relational algebra is same set difference operation as in set theory with the constraint that both relations should have same set of attributes.

**Set Intersection: **

Suppose there are two tuples R and S. The set intersection operation contains all tuples that are in both R & S. It is denoted by intersection ∩.

**Cross Product (X)**

Cross product between two relations let say R and S, so cross product between R X S will results all the attributes of R followed by each attribute of S. Each record of R will pairs with every record of S

**Rename (ρ)**

Rename is a unary operation used for renaming attributes of a relation. ρ (a/b)R will rename the attribute ‘b’ of relation by ‘a’.

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