In short, you can't - There is no mechanism baked into Tableau that will allow an outside data source to tell us to "refresh".
Are you doing this work in Tableau Desktop or Tableau Server? In Server you could "auto-refresh" by having the web page in which the visualization lives refresh itself.
I am using tableau desktop.
i will explain you the scenario.
I am developing dashboards which will be delivered to the client.
I have connected in "Live mode" to the sql server database.
But whenever there is a change in data in the database it has no impact on the report.
but when i am doing the same thing with EXCEL as a database it is working fine.
Moreover if i connect to the same table and import / connect live again i am getting the old data .(Whcih dont even exist in the table)
but the actual data in the table has been updated manually in sql server.
i am getting a weird problem.:(
Can you describe the exact steps that you're taking to make the "second connection"? Please be as specific as possible. Feel free to take screenshots, etc...you can insert them right into your reply.
Tableau Desktop does cache data on the client side to make fewer round-trips to the server, and I'd guess that cached rows are what you''re seeing. However, it makes no sense you're seeing caching on a completely different connection.