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...