I study SQL because after I start to work , necessary to use it. I suppose the book about SQL is sometimes boring and difficult to continue. so, I will introduce Progate and Udemy.
So, first about Progate, Progate is for beginner of programming. We can learn some languages with slides, and run the code on the browser. This service try to reduce the difficulty of beginner.
Especially, the quality of SQL is really good. Progate offers three courses, and one practice course. The below(sorry this is Japanese but about Where, or something) is about contents. The price is quite cheap, so check it out.
but, progate is not enough to learn all about SQL, because on Progate, we just write the code on browser, and do not have to try to build the environment and import data. So, I will recommend you to take Udemy’s SQL course. The course title is The complete SQL Bootcamp. Udemy always bargain the course, so I can buy it quite cheap price.
The contents is quite enrichment, you can learn SQL command, how to create database, etc!!
After the course completion, you can get the certificate.