which query is faster?

[wxdqz]

Does anyone know if it makes a diff to "select *" on a table or to select on a specific column name?

specifically, I'm trying to find out if there's a difference between the two queries:

select * from index_word where word = 'something';

select word_id from index_word where word = 'something';

I'm running queries like this a bunch of times so even a small diff would matter.

Matt.