Selecting most recent and specific version in each group of records, for multiple groups

Question

To get only latest revisions:

SELECT * from t t1
WHERE t1.rev = 
  (SELECT max(rev) FROM t t2 WHERE t2.id = t1.id)

To get a specific revision, in this case 1 (and if an item doesn’t have the revision yet the next smallest revision):

SELECT * from foo t1
WHERE t1.rev = 
  (SELECT max(rev) 
   FROM foo t2 
   WHERE t2.id = t1.id
   AND t2.rev <= 1)

It might not be the most efficient way to do this, but right now I cannot figure a better way to do this.