Results 1 to 2 of 2
  1. #1
    Join Date
    Feb 2006
    Posts
    18

    how to represent constraints in an ER diagram?

    I WOULD LIKE TO KNOW HOW TO REPRESENT ANY KIND OF CONSTRAINT IN AN ER DIAGRAM?
    CAN WE REPRESENT EVERYTHING IN AN ER DIAGRAM i.e EVERY CONSTRAINT CAN IT BE REPRESENTED IN AN ER DIAGRAM?IF SO HOW?
    ARE THERE ANY SET OF RULES WHICH WE CAN FOLLOW AND TELL WHETHER A CONSTRAINT CAN BE REPRESENTED IN AN ER DIAGARM?

    I WOULD REALLY APPRECIATE IF SOMEONE GIVES ME PICTORIAL REPRESENTATIONS USING ER DIAGRAMS TO SHOW CONSTRAINTS.

    THANK YOU
    KRISHNA

  2. #2
    Join Date
    Sep 2002
    Location
    UK
    Posts
    5,171
    Not all constraints can be shown in an ER diagram. You can usually show the primary unique identifier, and of course foreign keys (as relationships). You can also show cardinality rules on relationships. You can't show check constraints and multi-table constraints other than foreign keys (such as: "no two periods of assignment for an employee may overlap")

    I can't help with the pictorial examples, as I personaly use Barker notation which seems to be peculiar to Oracle and is probably not what you would be using.

    BTW, is your CAPS LOCK KEY STUCK DOWN?

Posting Permissions

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