Read Data into Tableau

Data Connection

Tableau refers to reading a data file as “connecting to the data”. A connection to the data file is required to read the data. However, the term connection alone does not adequately describe the process. Tableau does more than just connect to the data file. Once connected, it also reads the data into the current Tableau process for further analysis.

Open the Tableau app. The Connect tab in the left margin invites you to open a data file in a specified format, shown in Figure 1. Here, select an Excel formatted data file.

If you wish to follow along doing the Tableau data reading, find the file online.)

Figure 1: Connect to the data.

When installed, Tableau creates a My Tableau Repository folder in your Documents folder. You can also create folders (directories) in the repository, or anywhere else in your computer file directory. Here, I created a folder named data in addition to the Datasources folder that Tableau created, shown in Figure 2.

Figure 2: Locate the data file.

Click on Open to read the data table into Tableau. The Excel worksheet is named d, which is the name of the data table adopted by Tableau.

The data table is then automatically displayed in the Data Source window pane, which can be manually accessed by the tab of the same name in the lower-left corner of the Tableau window.

NoteField

Reference for a variable in the terminology of relational database, adopted also by Tableau .

The variables, or fields, are listed first. The following are the first rows of the data table, shown in Figure 3.

Figure 3: Data display in the Data Source tab.

Not all data values were present in the original Excel data file.

NoteTableau missing data code

null indicates a missing data value.

The blank cells in an Excel file are replaced with null for the Tableau representation.

Multiple Excel Worksheets

When Tableau opens an Excel file with multiple worksheets, the worksheets are listed, and you need to select at least one as a data source. To select, drag the worksheet name into the center of the window.

Figure 4: An Excel data source with two worksheets.

TipRelational database option

If you select more than one worksheet, Tableau lets you set up a relational database in which the tables are related by a unique ID shared by both.

When multiple data tables are selected, Tableau lists them under the Data tab by name, as shown in Figure 5. If only one data table is present, it is not named.

Figure 5: From multiple Excel worksheets, multiple data tables.

Ready to Visualize

The next step visualizes the data. To begin that analysis, open a new Tableau worksheet. Tableau prompts you for that step with the message in the lower-left corner of the data display window, shown in Figure 6.

Figure 6: Prompt to open a new worksheet.

Click on Sheet1 and move on to data visualization. Return to the Data Source tab at any time to view the data.