Data Source Page
Before or during your analysis, you may want to make changes to the Tableau data source. You can do that on the data source page. Tableau takes you to the data source page after you establish the initial connection to your data. You can also access the data source page by clicking the Data Source tab from any location in the workbook.
Although the look of the page and the options available vary depending on the type of data that you are connected to, the data source page generally consists of four main areas: left pane, canvas, data grid, and metadata grid.
Left pane
The left pane of the data source page displays details about your data – the data that Tableau Desktop is connected to.
For file-based data, the left pane might display the file name and the worksheets in the file.
For relational-based data, the left pane might display the server, the database or schema and the tables in the database.
You can also use the left pane to add more connections to the data source to create cross-database joins.
The left pane does not display for cube (multidimensional) data.
Canvas
When connected to most relational and file-based data, you can drag one or more tables to the canvas area to set up your Tableau data source. The canvas now has two layers: a logical layer and a physical layer. The default view shows the logical layer, which uses relationships between logical tables. To go to the physical layer, double-click a logical table in the logical view and create joins and unions between tables in the physical layer. For more information, see Tableau Data Model.
When connected to cube data, the top of the data source page displays the available catalogue or queries and cubes to select from to set up your Tableau data source.
Note: Depending on the type of data you are connected to, you can refresh your data when that data has changed using a number of options. For example if connected to a data extract, you can refresh a selected extract using the Refresh button 
that appears next to the Connection area in the left side of the pane. For more information about refresh options see Refresh Data Sources(Link opens in a new window). For more information about refreshing data extracts, see Refresh Extracts(Link opens in a new window).
Refreshing your data source
Depending on the type of data you are connected to you can refresh your data when that data has changed using a number of options. For example if connected to a data extract,
Data grid
Use the data grid to review the fields and the first 1,000 rows of the data contained in the Tableau data source. You can also use the data grid to make general modifications to the Tableau data source like sorting or hiding fields; renaming fields or resetting field names; creating calculations; changing the column or row sort; or adding aliases. For the Web Data Connector, file- and relational-based data sources in Extract mode, you can see extract data in the grid, including extract only calculations.
When you're in the logical layer, you see the data for the selected table.
In the physical layer, you see the merged data based on the joins and unions.
To select multiple fields in the grid, click a column, and then drag the mouse to select more columns.
To select all fields, click the area in the upper-left corner of the grid like in the example, below.
The grid is not displayed for cube (multidimensional) data.
Metadata grid
Depending on the type of data that you are connected to, click the metadata grid button to navigate to the metadata grid. The metadata grid displays the fields in your data source as rows so that you can quickly examine the structure of your Tableau data source and perform routine management tasks, such as renaming fields or hiding multiple fields at once.
When connected to cube or some extract only data, the metadata grid displays by default.