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Some API endpoints return JSON data where each value is nested under different keys that change between responses. This creates problems when mapping response fields to an output table.

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The problem

For example, if calling a currency conversion API gives us this JSON: 
{
  "base": "EUR",
  "start_date": "2020-01-01",
  "end_date": "2020-01-07",
  "rates": {
    "2020-01-01": {
      "USD": 1.1221,
      "GBP": 0.8462
    },
    "2020-01-02": {
      "USD": 1.1221,
      "GBP": 0.8466
    },
    "2020-01-03": {
      "USD": 1.1171,
      "GBP": 0.8495
    }
  }
}
When mapping this response using field mapping, we get a different field name for each date key under rates. For example, rates.2020-01-01.USD and rates.2020-01-02.USD would be treated as separate fields. If we change the request parameters to use different dates (like 2021-01-01 to 2021-01-03), we get completely new keys under rates that won’t map to any existing fields: 
{
   "base":"EUR",
   "start_date":"2021-01-01",
   "end_date":"2021-01-03",
   "rates":{
      "2021-01-01":{
         "USD":1.217582
      },
      "2021-01-02":{
         "USD":1.2135
      },
      "2021-01-03":{
         "USD":1.223409
      }
   }
}

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The solution

What we really want is just two consistent fields: a Date field and a USD field. We want different dates to appear as separate records with these same two fields. We can do this by denormalizing the response. We set:
  1. Denormalize Path to $.rates (the JSONPath expression for the top-level rates key)
  2. Denormalize Field Name to Date
After denormalization, the response becomes: 
{
  "base": "EUR",
  "start_date": "2020-01-01",
  "end_date": "2020-01-07",
  "rates": [
    {
      "Date": "2020-01-01",
      "USD": 1.1221,
      "GBP": 0.8462
    },
    {
      "Date": "2020-01-02",
      "USD": 1.1221,
      "GBP": 0.8466
    },
    {
      "Date": "2020-01-03",
      "USD": 1.1171,
      "GBP": 0.8495
    }
  ]
}
Now all dates appear under a consistent rates.Date field and all USD exchange rates appear under a consistent rates.USD field. This gives us stable field names that we can reliably map to our output table.

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How to denormalize the response

  1. On the create screen, scroll to the bottom and click to open the Advanced Settings.
  2. Under Denormalize Path, enter the JSONPath to where you want to denormalize the data (for the example above, use $.rates).
  3. Enter a Denormalize Field Name for the field that will be added to each record (for the example above, use Date).