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  1. #1
    Join Date
    Jan 2008
    Posts
    1

    ER Diagram Problem

    Hello everyone

    I am an IT student from Greece and i would like your help regarding a Data Base exercise.
    I would be greatful if you could guide me to clarify some points


    The Data Base Case is the following:

    The DB maintains historical information (for all the school years)
    for each school unit, for the total of elements that are presented
    below:

    • the elements of region where the school unit belongs are
      registered with the following form: <district,province,
      municipality, municipal department, area
      >
    • the further elements that are stored for each school unit
      are the < name, SUcode, Telephone, fax, email, postal address,
      elements of the director
      (the director of unit is a schoolperson
      with exclusively organic place in the unit).
    • for each schoolperson the data base maintains the
      <SPcode, name, surname, mother’s name, father’s name,
      specialty, and SSN
      >.
      Also is maintained the information of the
      organic place of the schoolperson (each schoolperson belongs in
      only one school unit "organically".......) as well as the
      information of all school units that the schoolperson are occupied
      (...while they could be occupied in more than one unit, with
      hours (per week) that should be working in his organic school
      unit. If for some reason this hours aren't covered , then the
      schoolperson could be able to be disposed or detached to another
      school unit, with obligation of occupation of certain additional
      hours.
    • The DB maintains elements of students (one unique code,
      name, surname, mother’s name, father’s name
      ), the class where
      they belong to in each school year, the elements of their school
      unit and the final degree in all the courses, per school
      year.



    My question is how to draw in an ER Diagram the realation between the
    schoolperson an the school unit so the DB can keep both the
    information of the organic place of a schoolperson and the
    information of the school unit he/she is disposed or detached and
    the relative hours

    Thank you in advance

  2. #2
    Join Date
    Jun 2004
    Location
    Arizona, USA
    Posts
    1,848
    Hmmm. Sounds as if there may be a many-to-many relationship between school person and school unit?
    Lou
    使大吃一惊
    "Lisa, in this house, we obey the laws of thermodynamics!" - Homer Simpson
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  3. #3
    Join Date
    Sep 2008
    Posts
    38
    How can there be many-many relation between school unit and school person?

    One school unit has one school person allocated organically
    One school person can be allocated to other school unit if his hours are remaining

  4. #4
    Join Date
    Sep 2008
    Posts
    38
    I tried an ERD for the requirement, can anyone please tell me how far Iam correct!!
    Attached Thumbnails Attached Thumbnails example 13.jpg  

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