I was trying to formulate a sql query, that I now think is impossible :-(
I just thought, I'd run it by you before I give up - perhaps, you guys would have some ideas...
Suppose, I have a table like this
create table test ( stuff int, stamp timestamp );
Now, I want to count the occurences of each value of stuff in the table, but so that entries within 24 hours from each other count as one...
The closest I could think of is:
select stuff, count (distinct date_trunc ('day', stamp)) from test group by stuff;
This doesn't do exactly what I need though - for example, if one entry is one minute before midnight, and the other one is two minutes later, they'd get counted as 2, and what I am looking for is the way to get them collapsed into one as long as they are less then 24 hours apart...
Now, I am pretty sure, it is simply impossible to do what I want with count (distinct...) because my 'equality' is not transitive - for example, three entries, like
A = 2001 - 01- 01 20:20:00
B = 2001 - 01 - 02 20:19:00
C = 2001 - 01 - 02 20:21:00
Should be counted as *two* (A === B, and B === C, but *not* A === C)...
Also, I could certainly write a simple function, that would get all the entries in order, and scan through them, counting according to my rules...
But I was hoping to find some way to do this in plain sql though...
Any ideas?
Thanks!
Dima
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