title: Get length of json array in SQL Server 2016
body: <p>You know about the new JSON_ support in SQL Server 2016 so
  let's say I have this data in a row</p>
  
  <pre><code>{
    "BaseBoarding": 1,
    "PriceLineStrategy": "PerPersonPerNight",
    "Currency": "EUR",
    "BasePriceLineList": [
      {
        "RoomTypeId": 1,
        "PeriodId": 1,
        "Price": 10.0
      },
      {
        "RoomTypeId": 1,
        "PeriodId": 2,
        "Price": 100.0
      },
      {
        "RoomTypeId": 1,
        "PeriodId": 3,
        "Price": 190.0
      },
      {
        "RoomTypeId": 2,
        "PeriodId": 1,
        "Price": 280.0
      },
      {
        "RoomTypeId": 2,
        "PeriodId": 2,
        "Price": 310.0
      },
      {
        "RoomTypeId": 2,
        "PeriodId": 3,
        "Price": 340.0
      }
    ]
  }
  </code></pre>
  
  <p>How do I get the number of items of "BasePriceLineList" in the most performant way, preferably using the built-in JSON support?</p>
  
  <p>Need to write something like this:</p>
  
  <pre><code>SELECT JSON_ARRLEN(JsonDataCol, '$.BasePriceline') FROM MyTable
  WHERE Id = 1
  </code></pre>
  
  <p>and get 6 as the result.</p>