QUERY: SELECT DISTINCT ON string4 two, string4, ten
	   FROM tmp
   ORDER BY two using <, string4 using <, ten using <;
two|string4|ten
---+-------+---
  0|AAAAxx |  0
  0|HHHHxx |  0
  0|OOOOxx |  0
  0|VVVVxx |  0
  1|AAAAxx |  1
  1|HHHHxx |  1
  1|OOOOxx |  1
  1|VVVVxx |  1
(8 rows)

