Enrolment

Hy all , i looking in moodle code and database and try to understand how moodle sql statments work when create a user , enroll a use to a course and create a course into a category ; I use moodle 1.9.2 and don,t visualize it;

tables are mdl_course_category mdl_course, mdl_role_assingnment , mdl_context , mdl_user ;

I just try understand the sql statments when a create a category and put create a course inside the , i realize a field path and sort order in md_course_category , its show the hierarqui ; But i want create a course into a category only with sql statments , and to enrol a user in this course only with sql , any solution?

Ps: I want create scripts for automatize course creation and student enrol only with SQL , I know how few tables work , but some how still dark ; Some help is useful here. Thanks.