Dorian Hoxha wrote > I have: create table tbl (a,b,c,d,e,f,g,h); > > And i need to select in 1 query ,or the most performant way: > > top 5(a) > top 5(b) > top 5(c): for each top5(c): top 5(d) > count(f) GROUP BY f > > > I can make these in separate queries but that means that postgresql would > read the table multiple-times? > > Is it possible/doable/sane ? > > Thanks Yes, it is - sorta. Create a custom array_agg like aggregate that only keeps the first 5 encountered values in the array and ignores all subsequent values. Then call that with order by. This gets you a,b,c,f You will need a separate query for the d output since that is dependent up the result of the c query. You should also try a window clause with appropriate partitions and compare the performance of the two. David J. -- View this message in context: http://postgresql.1045698.n5.nabble.com/Multiple-aggs-sums-in-1-query-tp5779761p5779775.html Sent from the PostgreSQL - general mailing list archive at Nabble.com. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
