MySQL admin with Ian Gilfillan

I was doing some reading today and I came upon an old series of articles over on www.databasejournal.com by a dude called Ian Gilfillan:

For the ‘type’ in SQL ‘EXPLAIN’ Ian says: from best to worst the types are: system, const, eq_ref, ref, range, index, all.
It seems this Ian Gilfillan fellow has been rather prolific.