/    /  SQL- Interview questions Part 3

1. What is normalization?

Answer: Normalization is the process of minimizing redundancy and dependency by organizing fields and table of a database. The main purpose of Normalization is to add, delete or modify field that can be made in a single table.


2. What is Denormalization.

Answer: DeNormalization is a technique used to access the data from higher to lower normal forms of database DeNormalization is also process of introducing redundancy into a table by incorporating data from the related tables.


3. What are all the different normalizations?

Answer: The normal forms can be divided into 5 forms, and they are explained below -.

1. First Normal Form (1NF):.

First normal form should remove all the duplicate columns from the table. It helps in Creation of tables for the related data and identification of unique columns.

2. Second Normal Form (2NF):.

Meeting all requirements of the first normal form. It helps in placing the subsets of data in separate tables and Creation of relationships between the tables using primary keys.

3. Third Normal Form (3NF):.

This should meet all requirements of 2NF. It helps in removing the columns which are not dependent on primary key constraints.

4. Fourth Normal Form (3NF):.

It should not have multi- valued dependencies and must meet all the requirements of third normal form.


4. What is a View?

Answer: A view is a virtual table which consists of a subset of data contained in a table. They are not virtually present, and it takes less space to store. It can have data of one or more tables combined, and it is depending on the relationship.


5. What is an Index?

Answer: An index is performance tuning method of allowing faster retrieval of records from the table. It creates an entry for each value and it will be faster to retrieve data.