Best place to get SQL programming certificate for online work?

Hi there! I currently work online 6 hours a day for 5 days a week as a graphics designer, and creating landing pages in Kajabi. I have a lot of time in my hands, so I would I like to take advantage of it by learning or rather re-learning SQL programming. I already have work experience with MySQL working in IT for 2 years, but that was already 3 years ago.

So I am trying to look for a place where I can get certified with it and hopefully use it to find more work online. Thank you!