A database for the Service and Maintenance (SM) section of a Computer sales and service Company has to be developed. SM gives after sales service to customers. SM branch has a number of employees (a manager, a number of operation executives & a number of service engineers). The SM will have branches in the four regions, South, North, East and West. Every branch has its branch number, address and region. A Manager is in charge of a branch.
An employee is identified by an employee number, name, address, date of joining and salary. Operation executives get the service requests from the customers by telephone lines or via Internet. Operative executives work in shifts (day / night shift). Operation executives allot the service requests to the Service Engineers. Service Engineers attend the service requests. A service engineer has a skill set and year of experience.
A Customer is recognized by customer number, name, address, e-mail address and telephone numbers. A customer may be member or a non-member. As a member of SM, customers are eligible to get a discount based on the accumulated service history that the customer has with SM. The service history of a customer is recorded by various service engineers.
SM is to satisfy all the customers with their differing service requirements of both types of services (Hardware & Software).
The branch gives necessary spare parts to service requests. Every spare part has unique spare part number, name and quantity on hand. Every branch is permitted to stock the spare parts of many vendors. SM always has sufficient number of spare parts and service engineers. SM will always maintain the balance of their spare parts by being continuously supplied by the vendors. A vendor has a name, address and unique number. A vendor may supply various spare parts to many branches.
Design of centralized relational database using Top down method.
In the design of a database using top down method, the 1st step is drawing the conceptual model (EER diagram) and 2nd step is translating the EERD into relational schema.
Drawing EERD:
With reference to the case study given above, perform the following tasks:
(a) Recognize all the real world entities giving a candidate key and suitable attributes for each entity.
(N.B. A maximum of 6 attributes should be given for each entity).
(b) Recognize an entity with a multi-valued attribute.
(c) Recognize a weak entity present in the case study and determine its relationship with the owner entity.
(d) Recognize the Super/ subtype entity available in the given scenario.
(e) Recognize any one possible ternary relationship in the given scenario.
(f) Sketch a complete EER diagram.