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

CUSTOMER CustomerID Surname Given DOB Sex PhoneHome PhoneWork PhoneFax Address Suburb State Postcode

 

CALLS CallsID MobileID CalledNumber CallDate CallTime CallDuration DataUsage 

 

MOBILE MobileID PhoneNumber BrandName Joined Cancelled PlanName PhoneColour CustomerID StaffID

 

STAFF StaffID Surname Given DOB Sex Joined Resigned Address Suburb Postcode Phone SupervisorID Commission RatePerHour

 

TOWER TowerID Location Bandwidth MaxConn SignalType

 

CONNECT ConnectID TowerID CallsID

 

PLAN PlanName BreakFee DataAllowance MonthlyFee PlanDuration CallCharge

Did any customer break their mobile plan before the mobile plan duration ends? Assume the plan duration is in months. Justify your answer with an SQL query by producing a list of customers who cancelled the plan before the duration expires. 

Answer rating: 100% (QA)

SELECT c Customer ID cSurname cGiven m Plan... View the full answer