If you are a novice and not from a CS background, it takes two to three weeks to learn SQL basics. I recommend starting with online courses because instructors will explain the basic principles which help you learn SQL faster. There are many SQL tutorials to understand the SQL Basics. After that, you can easily learn the advanced SQL topics. Then, start applying for entry-level jobs.
If you want to start a career in SQL, then check SQL Certification Course by Intellipaat.