MySql multiple columns using one alias

MySql multiple columns using one alias

I saw the following code:
SELECT u.ID, u.username, u.active, u.email, u.admin, u.banned, u.name AS
groupmemberships FROM users u WHERE u.ID={$uid}
and was wondering where the official documentation about aliasing multiple
columns was. W3schools (not the best source) as the only place where I
found "documentation" in the following way:
SELECT column_name(s)FROM table_name AS alias_name;
http://www.w3schools.com/sql/sql_alias.asp
I would appreciate a link to official documentation so I can look it over.