{
  "columns": [
    "invoiceDate$yearMonth",
    "sum(invoiceAmount) as totalAmount",
    "count(invoiceId) as billCount"
  ],
  "slice": [
    {
      "field": "invoiceDate$id",
      "op": "[)",
      "value": [
        "2012-01-01",
        "2013-01-01"
      ]
    }
  ],
  "groupBy": [
    "invoiceDate$yearMonth"
  ],
  "orderBy": [
    "invoiceDate$yearMonth"
  ],
  "limit": 100
}