hi guys ,

the following image showing Tables relations for billing system

billing_diagram.JPG

- customer can take many service

- service can take many promotions

-i bill customer every month , 3 months ,6 months , year

- maybe customer get discount 50% in first three months .. this is example of promotions

etc ...

* are the relations between DB tables correct ?
* credit , charge and balance in correct table ?
* names of columns is it correct ?


please help me , am some lost

regards