# DataBase Management Systems

## Second Normal Form (2NF)

Second Normal Form:   Before we learn about second normal form, we need to understand the following: Prime attribute: an attribute, which is part of prime-key, is prime...

## First Normal Form (1NF)

First Normal Form: This is defined in the definition of relations (tables) itself. This rule defines that all the attributes in a relation must have atomic domains. Values in...

## Normalization

Normalization If a database design is not perfect it may contain anomalies, which are like a bad dream for database itself. Managing a database with anomalies is next to...

## Trivial Functional Dependency

Trivial Functional Dependency Trivial: If an FD X → Y holds where Y subset of X, then it is called a trivial FD. Trivial FDs are always hold. Non-trivial:...

## Armstrong’s Axioms

Armstrong’s Axioms If F is set of functional dependencies then the closure of F, denoted as F+, is the set of all functional dependencies logically implied by F. Armstrong’s...

## Armstrong's Axioms

Armstrong’s Axioms If F is set of functional dependencies then the closure of F, denoted as F+, is the set of all functional dependencies logically implied by F. Armstrong’s...

## Functional Dependancy

Functional Dependancy A functional dependency is an association between two attributes of the same relational database table. One of the attributes is called the determinant and the other...

## Views

Views We have assumed up to now that the relations we are given are the actual relations stored in the database. For security and convenience reasons, we may wish...

## Modifying the Database- deletion, insertion, updating

Modifying the Database Up until now, we have looked at extracting information from the database. We also need to add, remove and change information. Modifications are expressed using the...

## The Domain Relational Calculus

The Domain Relational Calculus Domain variables take on values from an attribute’s domain, rather than values for an entire tuple.   Formal Definitions An expression is of the form...