DB SQL Queries

Dears, 

Appreciate if someone could give me useful SQL queries to be executed on Moodle LMS DB for the following business operations:

1- Validate if the user registered as Student or not.

2- Check if user "Student" already logged-in in LMS Portal or not.

2- Insert new user as student.

3- Get all courses categories.

4- Get all courses.

5- Get all registered courses for specific user "Student".

6- Enroll/Register the user "Student" for specific course.

7- UnEnroll or delete user "Student" registration from specific course.   

Thanks in advance.

Best Regards,

Rami Zaitoun