Methods to gain access a website's database?

Hello mates,
I was wondering what are the methods you can use to gain access to a website’s database as a Web App Pen tester?
Here are three methods I use:

  1. shell upload via upload file vunurability(burp suite)
  2. bruteforcing phpmyadmin login of the website
  3. mysql injection via mysqlmap

Please any other suggestions will be helpful to the community, thanks.