Get values from first and last row per group

Question

I\'m new to Postgres, coming from MySQL and hoping that one of y\'all would be able to help me out.

I have a table with three columns: name, week

Answer 1

This is a bit of a pain, because Postgres has the nice window functions first_value() and last_value(), but these are not aggregation functions. So, here is one way:

select t.name, min(t.week) as minWeek, max(firstvalue) as firstvalue,
       max(t.week) as maxWeek, max(lastvalue) as lastValue
from (select t.*, first_value(value) over (partition by name order by week) as firstvalue,
             last_value(value) over (partition by name order by week) as lastvalue
      from table t
     ) t
group by t.name;