Relational Operations 

Relational operations in a Database Management System (DBMS) are fundamental operations that are applied to relations (tables) in a relational database. These operations are essential for querying and manipulating the data stored in these tables. The primary relational operations are based on set theory and are used in conjunction with SQL (Structured Query Language). Here’s an overview of the key relational operations:

Types of Relational operation

1. Select Operation:

• he select operation selects tuples that satisfy a given predicate.
• 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. These relational can use as relational operators like =, ≠, ≥, <, >, ≤.

2. Project Operation:

• This operation shows the list of those attributes that we wish to appear in the result. Rest of the attributes are eliminated from the table.
• It is denoted by ∏.

Notation: ∏ A1, A2, An (r)

Where

A1, A2, A3 is used as an attribute name of relation r.

3. Union Operation:

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

A union operation must hold the following condition:

• R and S must have the attribute of the same number.
• Duplicate tuples are eliminated automatically.

4. 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 ∩.