July 25th, 2011, 05:59 AM
Need help with easy Entity Relationship diagram...
I saw a few posts on here about E-R diagrams and would be very grateful to anyone who can help me out.
I have a entity relationship diagram, the following conditions have to be satisfied/are true:
each tenant can rent a room in a hall of residence OR apartment.
lease agreements are made at the start of each year.
(hall of residence = 1 person to each room)
(apartment = 3 people to each room)
apartments are inspected by a accomodation officers (members of staff)
heres the link:
(replace the "xx" with "tt")
Is the diagram correct?
July 29th, 2011, 08:16 AM
IMHO this is not a ER-Diagram. I suggest to take a look to DIA software, you can found it on THIS link. Under the options you will find ER mode.
A ER diagram shows the entities, like the objects in a OO programming. In your case the entities could be the ROOMS, STAFF_MEMBERS. A relation is something like a conjunction for entities. In your case it could be INSPECTED for these 2 entities.
To create a correct ER, you have first to find out WHAT you want to store, second how to put all toghether (relations). The last part is to find common fields and define primary/secondary keys.
Try...and let me know.