is this app useful for someone looking to become a DBA with no prior knowlege in this field?

Answer 1

The SQL module here just teaches you the basics according to my opinion. You will learn how to write simple queries and thats it

Answer 2

As Nadeem said, you'll get a basic understanding of SQL. Afterwards, you'll want to seek out other resources to further learn, and you'll want to do a lot of practicing with it so you can become good at writing queries.