Learn SQL

There are some good SQL courses on datacamp.com too.

You can also consider free/paid courses on https://academy.vertabelo.com/.

Practice

The best practice you can get is by downloading and installing a SQL server service on your laptop/desktop. One suggestion is https://dev.mysql.com/downloads/. Download the mySQL Installer for Windows (assuming you use Windows 10/11) and install mySQL Server and mySQL Workbench. Use YouTube Search for video instructions if you need help!

Then, setup a Employee Database using resources available in https://dev.mysql.com/doc/employee/en/.

Connect to this database using the Workbench to do your SQL practice!

Also check https://www.sqlnoir.com/.