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  1. #1
    Join Date
    Nov 2008

    Help with e/r model.

    Hi everybody..

    I'm currently working on a college assignment to design a database to store data for a triathlon.

    The first stage is to use the e/r model to discuss possibilities for entities and and relationships..

    What exactly do I need to put in this section? I've come up with some thaughts on what data (times,teams etc..) I will be storing ad also a simple relationship table..(attached)

    In the brief i've been told to give examples of Unary, Ternary and Binary relationships.. I'm not really sure what these are..but i'll make an attempt. Could you help me identify some please..?

    Also I would appreciate some pointers on how I could improve this sketch as my ability to identify relationships isn't great..

    Quick Overview of my business rules..

    • Triathlon consists of Swim, Cycle, Run
    • Time is stored for each of the above sections
    • Two transition times:
    • from water and onto bike
    • get off bike and begin run
    • each participant(team) is issued with overall time..
    • two types triathlon:
    • Sprint tri
    • try-a-try
    • Regardless of type, swim goes of in waves of 30
    • delayed by 10-15 mins between each wave

    I greatly appreciate any help as Im pretty lost with the design side of things, sql is pretty good thank god!


    EDIT: Startgrid tables is supposed to be related to team table, not times table, oops!
    Attached Thumbnails Attached Thumbnails first e-r drawing.jpg  

  2. #2
    Join Date
    Apr 2002
    Toronto, Canada
    i don't understand bubbles

    were you told what modelling/diagramming style or convention to use for this assignment?

    i'm only comfortable with the style where the entity is in a box, and the relationships are lines between boxes | @rudydotca
    Buy my SitePoint book: Simply SQL

  3. #3
    Join Date
    Nov 2008
    Thanks for the quick response..

    We haven't been told about any conventions..sorry if its not drawn properly, it was only a quick mockup on smartdraw..My first ever drawing with it.

  4. #4
    Join Date
    Jun 2003
    Rudy, that's because you work primarily with MySQL.
    SQL Server uses either bubbles or rectangles, though the bubbles are leftover from the old Sybase octagon standards.
    Interestingly, Oracle 12c will be extended to accept any trapezoid, acute or obtuse, but will require a series of emoticons as connectors to denote the various relationships.
    If it's not practically useful, then it's practically useless.

    blindman "sqlblindman"

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