Subject PSQL: Getting both aggregation and individual rows
Author Josef KokeŇ°
Hi!

Is there a simple way to get an aggregation of some query as well as the
individual rows from within a PSQL? I.e., I have a stored procedure
GEN_DATA which produces individual rows (ID, Name, DateAndTime, Value).
I am processing the output of GEN_DATA in another stored procedure
PROCESS_DATA:

FOR SELECT id, name, dateandtime, value
FROM gen_data(...)
INTO ...
DO ...

Within this loop, I need the individual records, but I also need some
aggregations on them, i.e. MIN(dateandtime) or SUM(value). If I could
run GEN_DATA twice, then it would be easy (in the first run I would
calculate the aggregations, in the second run the individual values),
but I can't. If I could perform the processing in my application (rather
than the stored procedure), it would be easy, too (I would simply
traverse the result dataset of GEN_DATA twice), but again I can't do
that. Would Common Table Expressions or perhaps Derived Tables help me?

Thanks,

Josef