select convo_id, timestamp, count(*)
from messages
where timestamp < 1389225600 and convo_id = 7897

Heute: 65

select convo_id, timestamp, count(*)
from messages
where timestamp > 1389744000 and convo_id = 7897 and timestamp < 1389225600

15.: 682
14.: 717
13.: 663
12.: 625
11.: 420
10.: 44
09.: 0
08.: 0
07.: 37
06.: 5
05.: 36
04.: 0
03.: 0
02.: 0
01.: 0