teniendo estos datos
id,uni,la,lo,fr,hr
1,1,37.785835,-122.406418,2012-10-17,23:58:05
2,2,40.785835,-99.406418,2012-10-18,10:58:05
3,3,25.785835,-120.406418,2012-10-18,14:58:05
4,1,23.785835,-88.406418,2012-11-27,23:58:05
5,2,23.785835,-111.406418,2012-10-27,22:58:05
6,3,54.785835,-34.406418,2012-10-27,18:58:05
yo esperaria obtener este resultado
uni,la,lo
1,23.785835,-88.406418
2,23.785835,-111.406418
3,54.785835,-34.406418
ya que por cada valor de "uni" son los valores mas actuales de "la" y "lo"