Question

I’m trying to find a way to use Perl to further process a PostgreSQL output. If there’s a better way to do this via PostgreSQL, please let me know. I basically need to choose certain columns (Realtime, Value) in a file to concatenate certains columns to create a row while keeping ID and CAT.

First time posting, so please let me know if I missed anything.

Input:

ID  CAT   Realtime  Value
A   1    time1       55
A   1    time2       57
B   1    time3       75
C   2    time4       60
C   3    time5       66
C   3    time6       67

Output:

ID  CAT  Time                   Values
A   1    time 1,time2           55,57
B   1    time3                  75
C   2    time4                  60
C   3    time5,time6            66,67

Answer 1

You could do this most simply in Postgres like so (using array columns)

CREATE TEMP TABLE output AS SELECT
  id, cat, ARRAY_AGG(realtime) as time, ARRAY_AGG(value) as values
  FROM input GROUP BY id, cat;

Then select whatever you want out of the output table.