1 of 1 people found this helpful
The answer will vary depending on if you are using a live connection or an extract.
First, ensure that you are not using custom SQL anywhere, if you have more complex needs, have your DBA create views.
If you are using a live connection, Tableau will only send for the columns it needs to fetch.
Before you create an extract, hide the columns that you don't wish to see after adding them into your workbook, or 'hide columns not in view'. Once you have removed the extra columns, then create your extract, it will create a smaller dataset. Further, you can add an extract filter to remove further data. An extract by far is the next step for improving your performance.
Here is a good article on improving performance.