SQL Database help.

Question

I made a customer ,product,sales,billing,distributor and supplier tables and i connected some of them using foreign keys ect.
Thus, task 1 ,2 and 3 are complete but im left with task 4 and 5. Could someone please complete task 4 and 5. Could you give me the syntax of a similar example so i could apply it to my database.

Task 1: The system should be able to keep the records of the sales that have been
made.
Task 2: Customers should be able to see the availability of the products on the
database.
Task 3: QAC should be able to purchase antiques from both individuals, wholesalers
and new items from distributors.
Task 4: The system should be able to reorder items that are out of stock.
Task 5: The system should be able to generate the bill for a customer.

I made

Answer 1

seems you are Not the only one who has this problem.
if you search in Q&A with "sql" you find similar posts.

try to use update trigger for your database
https://dev.mysql.com/doc/refman/5.7/en/trigger-syntax.html