Square provides a point-of-sale credit card processing system. Chances are you've used its card reader to make purchases at a local small business.

Google Data Studio is a simple dashboard and reporting tool. It's free and easy to use, but it lacks the sophisticated features of higher-end reporting software. Many of the connectors it supports are for Google products, but third parties have written partner connectors to a wide variety of data sources. Its drag-and-drop report editor lets users create about 15 types of charts.

Square offers multiple APIs, but its Connect API is the best way to pull data from its system. It provides calls for customers, transactions, checkouts, and a handful of other endpoints. To use it to list transactions for a particular location, for example, you would call GET /v2/locations/[location_id]/transactions.

The Square API returns JSON-format data. The data returned for a "list transactions" call might look like this:

{
  "transactions": [
    {
      "id": "KnL67ZIwXCPtzOrqj0HrkxMF",
      "location_id": "18YC4JDH91E1H",
      "created_at": "2017-11-20T22:57:56Z",
      "tenders": [
        {
          "id": "MtZRYYdDrYNQbOvV7nbuBvMF",
          "location_id": "18YC4JDH91E1H",
          "transaction_id": "KnL67ZIwXCPtzOrqj0HrkxMF",
          "created_at": "2017-11-20T22:57:56Z",
          "note": "some optional note",
          "amount_money": {
            "amount": 5000,
            "currency": "USD"
          },
          "processing_fee_money": {
            "amount": 138,
            "currency": "USD"
          },
          "type": "CARD",
          "card_details": {
            "status": "CAPTURED",
            "card": {
              "card_brand": "VISA",
              "last_4": "1111"
            },
            "entry_method": "KEYED"
          },
          "additional_recipients": [
            {
              "location_id": "057P5VYJ4A5X1",
              "description": "Application fees",
              "amount_money": {
                "amount": 20,
                "currency": "USD"
              }
            }
          ]
        }
      ],
      "refunds": [
        {
          "id": "7a5RcVI0CxbOcJ2wMOkE",
          "location_id": "18YC4JDH91E1H",
          "transaction_id": "KnL67ZIwXCPtzOrqj0HrkxMF",
          "tender_id": "MtZRYYdDrYNQbOvV7nbuBvMF",
          "created_at": "2017-11-20T22:59:20Z",
          "reason": "some reason why",
          "amount_money": {
            "amount": 5000,
            "currency": "USD"
          },
          "status": "APPROVED",
          "processing_fee_money": {
            "amount": 138,
            "currency": "USD"
          },
          "additional_recipients": [
            {
              "location_id": "057P5VYJ4A5X1",
              "description": "Application fees",
              "amount_money": {
                "amount": 100,
                "currency": "USD"
              }
            }
          ]
        }
      ],
      "reference_id": "some optional reference id",
      "product": "EXTERNAL_API"
    }
  ]
}

If you don't already have a data structure in which to store the data you retrieve, you'll have to create a schema for your data tables. Then, for each value in the response, you'll need to identify a predefined datatype (INTEGER, DATETIME, etc.) and build a table that can receive them. Square's documentation should tell you what fields are provided by each endpoint, along with their corresponding datatypes.

Complicating things is the fact that the records retrieved from the source may not always be "flat" – some of the objects may actually be lists. This means you'll likely have to create additional tables to capture the unpredictable cardinality in each record.

Google Data Studio uses what it calls "connectors" to gain access to data. Data Studio comes bundled with 17 connectors, mostly to pull in data from other Google products. It also supports connectors to MySQL and PostgreSQL databases, and offers 200 connectors to other data sources built and supported by partners.

Google Data Studio provides a graphical canvas onto which users drag and drop datasets. Users can set dimensions and metrics, specify sorting and filtering, and tailor the way reports and charts are displayed.

At this point you've coded up a script or written a program to get the data you want and successfully moved it into your data warehouse. But how will you load new or updated data? It's not a good idea to replicate all of your data each time you have updated records. That process would be painfully slow and resource-intensive.

Instead, identify key fields that your script can use to bookmark its progression through the data and use to pick up where it left off as it looks for updated data. Auto-incrementing fields such as updated_at or created_at work best for this. When you've built in this functionality, you can set up your script as a cron job or continuous loop to get new data as it appears in Square.

And remember, as with any code, once you write it, you have to maintain it. If Square modifies its API, or the API sends a field with a datatype your code doesn't recognize, you may have to modify the script. If your users want slightly different information, you definitely will have to.