Maybe by using a sequence and a function. The sequece to generate the row number.
The a function 1) to reset the sequence and 2) to perform a select with the first column nextval(seq) and the column the timestamp However, I am a newbie with PostgreSQL and I am not sure it this will work correctly...you might have to play with it (or wait for somebody with more experience than me). Bernard On Wednesday 10 March 2004 16:23, Randall Skelton wrote: > >> I to return a sequential row number beginning at 1? > >> > >> i.e. > >> > >> row| timestamp > >> ---+---------------------------- > >> 1 2004-02-01 23:15:00.824-05 > >> 2 2004-02-01 23:15:01.824-05 > >> 3 2004-02-01 23:15:02.824-05 > >> ... > >> > >> My reason for wanting row numbers is so I can use a 'MOD(row_number, > >> n)' to get the nth row from the table. > > Correction, I don't want to simply get the nth row, I want all rows > that are divisible by n. Essentially, the timestamp is at a regular > interval and I want a way of selecting rows at different sampling > intervals. > > > Doesn't LIMIT and OFFSET do the job? > > http://www.postgresql.org/docs/7.3/interactive/queries-limit.html > > It would if I only wanted an offset butI want a query to return the > first, fifth, and tenth, and so on row. This would be 'MOD(row_num, > 5)' but given that I don't know the number of rows a priori, it is > difficult to write a LIMIT. Moreover, the offset doesn't make it easy > to get the first row. Unless, of course, I am missing something > obvious? > > Cheers, > Randall > > > ---------------------------(end of broadcast)--------------------------- > TIP 2: you can get off all lists at once with the unregister command > (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED]) ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend