# DataBase Management Systems

## Measures of Query cost

Estimation of Query-Processing Cost To choose a strategy based on reliable information, the database system may store statistics for each relation r: – the number of tuples in r....

## Overview Of Query Processing & Query Optimization

Query Interpretation Why do we need to optimize? A high-level relational query is generally non-procedural in nature. It says “what”, rather than “how” to find it. When a query...

## Overview Of Query Processing & Query Optimization

Query Interpretation Why do we need to optimize? A high-level relational query is generally non-procedural in nature. It says “what”, rather than “how” to find it. When a query...

## Fifth Normal Form (5NF)

Fifth Normal Form   A relation R is in Fifth Normal Form (5NF) if and only if the following conditions are satisfied simultaneously:   1.         R is already...

## Fourth Normal Form (4NF)

Fourth Normal Form (4NF) We saw that BC-schema was in BCNF, but still was not an ideal design as it suffered from repetition of information. We had the multivalued...

## Multivalued Dependencies

Multivalued Dependencies Functional dependencies rule out certain tuples from appearing in a relation.If A B, then we cannot have two tuples with the same A value but different B...

## Boyce-Codd Normal Form (BCNF)

Boyce-Codd Normal Form : BCNF is an extension of Third Normal Form in strict way. BCNF states that For any non-trivial functional dependency, X → A, then X must...

## Other Functional Dependencies

Other Functional Dependencies There are same rather types of functional dependencies, which play a vital rule during the process .of normalization of data.   Candidate Functional Dependency A candidate...

## Closure of a Set of Functional Dependencies

Closure of a Set of Functional Dependencies We need to consider all functional dependencies that hold. Given a set F of functional dependencies, we can prove that certain other...

## Third Normal Form (3NF)

Third Normal Form: For a relation to be in Third Normal Form, it must be in Second Normal form and the following must satisfy: No non-prime attribute is transitively...