The purpose of this exercise is to build some automation in our schema. Specifically, we want to make sure that when certain events occur, there are respective changes that happen downstream from the change to keep our overall schema healthy. Assignment: 1. Create a grades table with Student ID, Section ID and Grade. 2. When a student registers for a class, add a record to the GRADE table. This record should include the student ID and the section ID with no grade or null. 3. When a student is marked as inactive on the student table. All classes in which they were registered and have not received a grade should be marked as "D" or deleted.