SQL : Select Query : Distint Clause

Introduction:
The DISTINCT clause allows you to remove duplicates from the result set. The DISTINCT clause can only be used with select statements.

The syntax for the DISTINCT clause is:
SELECT DISTINCT columnsFROM tablesWHERE predicates;

Example #1
Let's take a look at a very simple example.
SELECT DISTINCT categoryFROM ebooks;

This SQL statement would return all unique categories from the ebooks table.

Example #2
The DISTINCT clause can be used with more than one field.
For example:

SELECT DISTINCT category, publisherFROM ebooks;

This select statement would return each unique category and publisher combination. In this case, the distinct applies to each field listed after the DISTINCT keyword.