# 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
• Since you are only changing the metadata, i.e. the name of the returned columns, it doesn't affect each row as it is processed. I'd expect the overhead to be inconsequential. – HABO Oct 5 '12 at 13:09