MySQL/Language/Alias

An expression and a column may be given aliases using AS. The alias is used as the expression's column name and can be used with order by or having clauses. For e.g. These aliases can be used in ORDER BY, GROUP BY and HAVING clauses. They should not be used in WHERE clause.

A table name can have a shorter name for reference using AS. You can omit the AS word and still use aliasing. For e.g. Aliasing plays a crucial role while you are using self joins. For e.g. people table has been referred to as p and c aliases!

MySQL/Alias