jq：根据 group by 计算嵌套对象值

Json:

    [
  {
  "account": "1",
  "cost": [
      {
         "usage":"low",
         "totalcost": "2.01"
      }
   ]
  },
  {
  "account": "2",
  "cost": [
      {
         "usage":"low",
         "totalcost": "2.25"
      }
   ]
  },
  {
  "account": "1",
  "cost": [
      {
         "usage":"low",
         "totalcost": "15"
      }
   ]
  },
  {
  "anotheraccount": "a",
  "cost": [
      {
         "usage":"low",
         "totalcost": "2"
      }
   ]
  }
]

预期结果：

account cost
1       17.01
2       2.25
anotheraccount cost
a              2

我能够提取数据，但不知道如何聚合它。

jq '.[] | {account,cost : .cost[].totalcost}'

有没有办法使用 jq 来做到这一点，以便我获得所有类型的帐户以及与之相关的成本？

两个辅助功能将帮助您到达目的地：

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) })
;

有了这些，以下调用：

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

yield:

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

您应该能够管理 jq 中的最终格式化步骤。