PRØV at vælge det maksimale ID grupper efter db_type først og derefter bruge den som underforespørgsel med not in .

 DELETE FROM MyTable 
 WHERE ID NOT IN 
    (SELECT ID FROM 
      (SELECT MAX(ID) AS ID from MyTable GROUP BY DB Type) AS tb1
    )

EDIT:

 DELETE FROM MyTable
 HAVING MAX(ID) > ID;