Database systems and models

Project description
Design a SQL query that will allow the finance department to determine commissions paid to specific employees of the sales department for the month of december. This will require generating the following tables with SQL: Employee, Invoice, Invoiceline, Product, Department, Job.

Determine and explain factors necessary for referential integrity. Create an object-oriented model to show how the tables are inter-related. Ensure the relationship type is clear in the diagram (1:M, 1:1, M:N)