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  1. #1
    Join Date
    Jul 2008
    Posts
    7

    Question newbie question.

    I know this may sound like a ridiculous question, as I somehow doubt it's even worth asking.

    But as I always like to be better safe than sorry, I'll ask anyway.

    Is it always mandatory that all entities in an entity relation diagram be related?
    I ask this because I'm modeling a database for a web Application I'm going to start to develop, and I have an entity-relation diagram with a log table and a related log-detail table, both of which aren't related to any other tables in the database.

    Originally I just placed them in the bottom of the diagram with the remaining related tables above them, but a coworker of mine just told me I have to relate them all, and It just doesn't feel right, as there aren't any other tables in the design that seem to be fit to be related with the log table.

    Opinions?

  2. #2
    Join Date
    Feb 2004
    Location
    In front of the computer
    Posts
    15,579
    An Entity Relationship diagram shows the Entities that you're schema has and the relationships between those Entities. I've never seen anything that specifies any limit on the number of relationships, zero or more has always been acceptable.

    At least based on that claim, your co-worker doesn't understand what ER diagrams are or how they are used.

    -PatP
    In theory, theory and practice are identical. In practice, theory and practice are unrelated.

  3. #3
    Join Date
    Jul 2008
    Posts
    7
    Thanks, that clears it up for me. this situation is weird for me because I've never come across any rule that dictates what he's telling me. I guess I'm gonna have to talk to him to resolve the issue.

    in any case, thank you.

  4. #4
    Join Date
    Jun 2003
    Location
    Ohio
    Posts
    12,592
    Your log tables are likely related to auditing, and as such may not be integrated into your application data table schema.
    Your co-worker has evidently read enough about database design to sound convincing, but not enough to actually understand what he is saying.
    If it's not practically useful, then it's practically useless.

    blindman
    www.chess.com: "sqlblindman"
    www.LobsterShot.blogspot.com

  5. #5
    Join Date
    Feb 2004
    Location
    One Flump in One Place
    Posts
    14,912
    +1 to Pat and blinman's points.
    Testimonial:
    pootle flump
    ur codings are working excelent.

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