Is there a performance difference using AS keyword in SQL? I'm working on a project in which the previous programmer seems to have loved using the AS keyword in the SELECT part of queries. I really don't like how it's written but if there is no performance difference I won't change existing code.

My tests did give a slight advantage to not using the AS keyword but I'm clueless on how to properly test it(I ran the different queries using Navicat)

And maybe there is also a difference between different types of databases and engines. I'm using MySQL InnoDB.

Simplified query:


SELECT DISTINCT
    `sometable`.`id` AS `id`,
    `sometable`.`name` AS `name`,
    `sometable`.`description` AS `description`,
    `sometable`.`price` AS `price`,
    `sometable`.`size` AS `size`,
    `sometable`.`area` AS `area`,
    `sometable`.`center` AS `center`
FROM `sometable`
I wouldn't expect much if any noticeable overhead as all that is doing is aliasing the name of the column in the result set.

The question I would ask however, is why it's being done in the first place? All I can think of is to prevent the code which uses the query breaking if a column is renamed (as long as the alias isn't changed).