jq: count nest object values based on group by

Question

Json:

    [
  {
  \"account\": \"1\",
  \"cost\": [
      {
         \"usage\":\"low\",
         \"totalcost\": \"2.01\"
      }
   ]
  },
  {
  \"account\":         


        

Answer 1

Two helper functions will help you get you to your destination:

def sigma( f ): reduce .[] as $o (null; . + ($o | f )) ;

def group( keyname ):
  map(select(has(keyname)))
  | group_by( .[keyname] )
  | map({(keyname) : .[0][keyname], 
          cost: sigma(.cost[].totalcost | tonumber) })
;

With these, the following invocations:

group("account"),
group("anotheraccount")

yield:

[{"account":"1","cost":17.009999999999998},{"account":"2","cost":2.25}]
[{"anotheraccount":"a","cost":2}]

You should be able to manage the final formating step in jq.