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Degree of participation RRS feed

  • Question

  • I am new to databases and Access, but I have been reading a book called Database Design for Mere Mortals by Michael Hernandez and it talks about setting the degree of participation (participation constraints?) between two tables, which is the minimum and maximum number of records that one table can have associated with a single record in a related table. But when I go to Access and try to do this, I have no idea how. Can this be accomplished in Microsoft Access? I have searched the net and have come up with nothing. Is it possible to set the degree of participation in Access? Any help or information would be appreciated. Thanks in advance. 

    Jay
    Monday, November 21, 2016 1:16 AM

All replies

  • Hi Jaydubya99,

    it looks like you are talking about Degree of Relationship.

    Degree of relationship refers to the number of participating entities in a relationship. If there are two entities involved in relationship then it is referred to as binary relationship. If there are three entities involved then it is called as ternary relationship and so on.

    On the other hand, it is the cardinality of relationship that defines the number of instances of one entity as it relates to the number of instances of the other entity.  Based on the different combinations between two entities we can have either one-to-one, one-to-many or many-to-many relationship.

    Following are the degrees of Relationships.
    1.   Single Entity - Unary
    2.   Double Entities - Binary
    3.   Triple Entities - Ternary
    4.   N Entities - N- ary

    Following are the types of Relationships.
    1. one-to-one
    2. one-to-many
    3. many-to-many

    it is concept that you can implement when you design the database.

    please visit the link mentioned below. in which you will get the idea how to implement this concept to design the database.

    Entity Data Model Relationships

    Regards

    Deepak


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    Tuesday, November 22, 2016 4:44 AM
    Moderator
  • An example of participation constraints might be:

    1.  An employee can work on a project.
    2.  An employee can be the leader of a project.

    The first is a many-to-many relationship type as multiple employees might work on each project and each employee might work on multiple projects.  This is a total participation constraint.

    The second is a many-to-one relationship type as each employee might be a leader of multiple projects, but each project can have one leader only.  This is a partial participation constraint.

    So, to model this you would create two relationship types between employees and projects, the first being modelled by a table which resolves the many-to-many relationship type into two one-to-many relationship types, the second by including an ProjectLeaderID foreign key in projects referencing the primary key EmployeeID of Employees.

    Ken Sheridan, Stafford, England

    Tuesday, November 22, 2016 12:32 PM
  • Hi Jay,

    I think Access only provides one way to set the degree of participation, and it's by setting referential integrity on the relationship. Unfortunately, the degree of participation is limited to none, one, or infinity.

    none: a foreign key of a child record can contain a null value to indicate no relationship with any parent records

    one: a child record can only be related to a specific parent record

    infinity (many): a parent record can be related to multiple child records (at least one)

    Just my 2 cents...

    Thursday, November 24, 2016 5:46 PM
  • Hi Jaydubya99,

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    Regards

    Deepak


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    Friday, November 25, 2016 5:28 AM
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