Is it worth it to learn SQL?

Leandro;

If you are going to stick/concentrate on front-end development you likely won't need to get that in depth to any database. Certainly having a good foundation as to how to do CRUD (Create, Read, Update, Delete) operations in a variety of databases in your chosen front-end language/framework would be highly beneficial.

In terms of how important is SQL versus NoSQL, it will often come down to your employer or client's needs. They both have their strengths and weaknesses so, again, at least being familiar with them enough to work with is important.

As a front-end developer you likely won't need to know, for example, how the difference in schema design impacts performance.

Post back with further questions.

Ken

I think it's definitely worth your time to study SQL. While more and more businesses/sites may be moving to NoSQL databases, I'd be willing to bet that the vast majority still use SQL based databases. So if you go to work for any company who has been established for a long time, chances are that they'll be using a SQL based database.

Hope this helps!