employer cover photo
employer logo
employer logo

Summitworks Technologies

Is this your company?

Summitworks Technologies Interview Question

What is normalization in SQL?

Interview Answer

Anonymous

Jun 16, 2017

Normalization is the systematic technique of organizing the data in the database by decomposing tables to eliminate redundancy and undesirable characteristics. - it is a multi step process that puts data into tabular form by removing duplicated data from the relation tables. Normalization is used for mainly two purpose, Eliminating reduntant(useless) data. Ensuring data dependencies make sense i.e data is logically stored. -Normalization rule are divided into following normal form. First Normal Form - no two Rows of data must contain repeating group of information i.e each set of column must have a unique value, such that multiple columns cannot be used to fetch the same row. Each table should be organized into rows, and each row should have a primary key that distinguishes it as unique. Second Normal Form - here must not be any partial dependency of any column on primary key. It means that for a table that has concatenated primary key, each column in the table that is not part of the primary key must depend upon the entire concatenated key for its existence. If any column depends only on one part of the concatenated key, then the table fails Second normal form. Third Normal Form - every non-prime attribute of table must be dependent on primary key, or we can say that, there should not be the case that a non-prime attribute is determined by another non-prime attribute. So this transitive functional dependency should be removed from the table and also the table must be in Second Normal form. For example, consider a table with following fields.

1