• A procedural query language which is used widely is known as Relational Algebra.
• Instances of relation are given as input data and we get output as occurrences of relations
• Relational algebra uses various operations to perform this input and output action.
• In a relation sql relational query operations are performed recursively.
• Output for the above operations is a new relation, which is formed from one or more input relations.

## Types of Relational Operation

### Select Operation

• Tuples that satisfy a given predicate is selected by select operation.
• It is denoted by sigma(σ).
• Notation:  σ p(r)
• Where (σ) is used for selection prediction.
• R is used for relation,
• p is used as a propositional logic formula which may use connectors like: AND OR and NOT.

### Project Operation

• List of attributes that wish to appear in the result is shown in project operation.
• Remaining attributes are eleminated from the table.
• It is denoted by ∏.

### Union Operation

• In union there are two tuples, R and S.
• The union operation that contains all the tuples are either in R or S or both in R & S.
• It eliminates the duplicate tuples. It is denoted by ∪.

### Notation: R ∪ S

• Following condition should be held by Union operation.
• R and S must have the attribute of the same number.
• Duplicate tuples are eliminated automatically.

### Set Intersection

• Let us consider 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 ∩.
• Notation: R ∩ S

### Cartesian product

• The Cartesian product is used to combine each row in one table with each row in the other table. It is also known as a Cross product.
• It is denoted by X.
• Notation: E X D

### Rename Operation

• The rename operation is used to rename the output relation. It is denoted by rho(ρ).

Categorized in: