Tableau connects directly to native data engines and also includes the option to extract data locally. The unique experience of working with data in Tableau is a result of Visual Query Language (VizQL).

VizQL was developed as a Stanford Research Project focusing on the natural ways by which humans visually perceive the world and how those ways can be applied to data visualization. We naturally perceive differences in size, shape, spatial location, and color. VizQL allows Tableau to translate your actions, as you drag and drop fields of data in a visual environment, into a query language that defines how the data encodes those visual elements. You will never need to read, write, or debug VizQL.

Tableau will generate the Visual Query Language behind the scenes as you drag and drop fields onto various shelves defining size, color, shape, and spatial location. This allows you to focus on visualizing data and not on writing code!

One of the benefits of VizQL is that it provides...

There is virtually no limit to the data Tableau can visualize. Each successive version of Tableau adds new native connections. Tableau continues to add native connectors for cloud-based data and recently included the Web Data Connector, which allows you to custom-build a connector for any online data you wish to retrieve. Additionally, for any database without a native connection, Tableau gives you the ability to use a generic ODBC connection. The Extract API allows you to programmatically extract and combine any data source(s) for use in Tableau.

You may have multiple data source connections to different sources in the same workbook. Each connection will show up under the Data tab on the left sidebar.

This section will focus on a few practical examples of connecting to various data sources. We won't cover every possible connection, but we will cover several that are representative of others. You may or may not have access to some of the data sources in the following examples...

Data sources in Tableau are a definition of the connection(s). In addition to storing information about the connection (such as database server name, database, and/or file names), the data source also contains information about all the fields available (such as field name, data type, default format, comments, aliases, and so on). Often, this data about the data is referred to as metadata.

Right-clicking on a field in the data pane reveals a menu of metadata options. Some of these options will be demonstrated in the following exercise, others will be explained throughout the book. The following are some of the options available via right-click:

Most data sources give the option of either connecting live or extracting the data; however, some cloud-based data sources do require an extract. Conversely, OLAP data sources cannot be extracted and require live connections.

When using a live connection, Tableau issues queries directly to the data source (or uses data in the cache if possible). When you extract the data, Tableau pulls some or all of the data from the original source and stores it in a Tableau Data Extract file (.tde). Extracts extend the way in which Tableau works with data. Consider the following diagram:

The fundamental paradigm of how Tableau works with data does not change, but you'll notice that Tableau is now querying and getting results from the extract. Data can be retrieved from the source again to refresh the extract. Thus, each extract is a snapshot of the data source at the time of the latest refresh. Extracts offer the benefit of being portable and extremely...