Is this a bug?

The following sql statement fails because the column "user_id" does
not exist in the users table.

=# select user_id from users WHERE  username = 'blah';
ERROR:  column "user_id" does not exist
LINE 1: select user_id from users WHERE  username = 'blah......
               ^

The following shows a valid statement where I want to delete one user
entry from the "map_users_roles" table

=# delete from map_users_roles where user_id = (select id from users
WHERE  username = 'blah');
DELETE 2

If I made a mistake and changed the "id" column to "user_id" then from
some the statement executes.

=# delete from map_users_roles where user_id = (select user_id from
users WHERE  username = 'blah');
DELETE 33631

I would have thought that the last statement would fail. Instead it
removed all the entries from the table. This is happening because I
did not qualify the column names as follows...

=# delete from map_users_roles where user_id = (select u.user_id from
users as u WHERE  username = 'blah');
ERROR:  column u.user_id does not exist
LINE 1: ...lete from map_users_roles where user_id = (select u.user_id ...

Still, this was quite a suprise to me and I would consider this a bug.

Thoughts?

--
Harry
http://www.uklug.co.uk
http://www.hjackson.org