Results 1 to 2 of 2
  1. #1
    Join Date
    May 2003
    Posts
    1

    Unhappy Please... Help with database project

    I am designing a simple database for a class which will track all of my expenses. The problem arises where I have an entity named WITHDRAWALS from bank accounts. Some, but not all, withdrawals go to an entity called CASH and some go directly to EXPENSES, and all ultamately end up in EXPENSES. How do I explain this using Business Rules and an E-R Diagram using Chen notation?

  2. #2
    Join Date
    Sep 2002
    Location
    UK
    Posts
    5,171

    Re: Please... Help with database project

    Originally posted by D5obrien
    I am designing a simple database for a class which will track all of my expenses. The problem arises where I have an entity named WITHDRAWALS from bank accounts. Some, but not all, withdrawals go to an entity called CASH and some go directly to EXPENSES, and all ultamately end up in EXPENSES. How do I explain this using Business Rules and an E-R Diagram using Chen notation?
    I don't think we have enough information to go on here. What would an entity called CASH look like? Does it mean the amount of money you currently have in cash (more like an attribute)?

    A guess would be:

    BANK ACCOUNT --< WITHDRAWAL >--< EXPENSE

    (This isn't Chen notation, unless by coincidence!)

    i.e. A WITHDRAWAL must be made against 1 BANK ACCOUNT;
    A BANK ACCOUNT may be subject to many WITHDRAWALS;
    A WITHDRAWAL may be allocated to one or more EXPENSES;
    An EXPENSE may allocated to one or more WITHDRAWALS;

    CASH is simply the total of WITHDRAWALS that have not been allocated to EXPENSES.

    Like I said, it's just a guess!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •