Data Base week4_1

16/02/2010

ERD: Entity Relationship Diagram

 
 

Scenario 1

Auckland Computers company Ltd

Auckland Computers company Ltd purchase parts from a variety of suppliers, both in NZ and overseas and use the parts to assemble a range of IBM compatible computers. Auckland Computers do not market directly to the public; they sell their machines to re-sellers such as Dick Smithers. Re-sellers fax orders to Auckland Computers who assemble computers on demand and dispatch the orders with packing slip. The resellers receive their invoice through the post and are encouraged to make payment within 20 days of receipt of invoice.

 
 

Way of drawing ERD

1. Understand business
   
2. Find a noun
   
3. Delete duplicate noun
   
4. Unique noun can't become entity. (only one attribute)
   

   Ex. Auckland Computer company Ltd.
   

5. General noun also can't become entity.
   

   Ex. Public, Overseas