Tableau could handle as much data in it as the data source could handle, that is the fact. There is no limit whatsoever on how many records that tableau could handle.
If you are interested in learning Tableau, start by checking out the Tableau tutorial, then check out Intellipaat’s Tableau certification course to help you get trained and get yourself prepared for the Tableau Desktop Qualified Associate certification exam.
Also, check out our YouTube video on Tableau training for beginners, if you are a newbie or if you are just starting out.