Maybe these are easier to understand if you consider the degenerate case where no partition is specified - then the whole table is one partition:
select seqnum, count(*) over () from doctor
gives you count(*) repeated on each row, a bit like Sybase used to do if you missed out the group by.
select seqnum, row_number() over (order by seqnum) from doctor
gives you the sort order number for each row when sorted by seqnum
Similarly, window aggregation functions work without an order by:
select seqnum, count(*) over (partition by doctor_seqnum) from episode
gives (repeated for each episode for a particular Doctor) the number of episodes featuring that Doctor. (You couldn't do row_number() here because it requires a sort).
Anti-nuisance lawsuit warning: The purpose of these notes is to remind me, Zoegond, of stuff or to help me work stuff out. They may contain mistakes.
Quick
- ($a, $b....) = unpack("A2A7...", $packed)
- push( array, list )
