7 Display the supervisor's details and the total number of staff they supervise.

8 List all the staff who are not supervisors.

9 Did the total number of calls increase during the COVID lockdown period (2020) compared to 2019? Substantiate your answer with an SQL query.

Assessment 2 Data Implementation - Case Study The following case study models a mobile phone company. The company has a number of phones that are sold by staff to various clients. Each phone comes with a plan and each plan has a number of features specific to that plan including: - a call charge in cents per minute (this does not apply to all plans) - a plan duration in months - a break fee if the customer leaves the plan before the end of the plan duration - a monthly data allowance in gigabytes Assumptions that are made for the assignment are: - mobile phones are locked to a plan for the length of the plan duration Entity-Relationship Diagram Relational Model