[JAVA] My site was thrown in a week after joining the company

I don't know how to study programming, so please teach me how to study.

I got a new graduate job in small and medium-sized IT in September 2017. There was almost no training for new employees in the company. Without knowing right or left, I was asked to do my best at the customer to which my senior employee belongs within about a week after joining the company. Of course, my seniors don't teach me the basics.

I understand how to use Java and SQL.

Therefore, I have studied at the following reference books and sites so far.

1. Clear Java 2nd Edition
2. Progate Java course

Reference books currently being studied and planned to be studied in the future

1. Java 2nd Edition Practical Edition Basics of Application Creation
2. Readable code
3. Why can't you do object-oriented development in Java?

I'm struggling because I don't know how to study SQL. I would like to know if there is any good way to study.