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Entity-Relationship Models

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      1 min de lecture

    • source

      llms.txt

    E/R model

    sketch databse schemas including constraints.

    • Entity set = rectangle
    • Attribute = oval, with a line to the rectangle (representing its entity set)

    relationship

    • connects two or more entity sets.
    • represented by a diamonds

    value of a relationship is a relationship set

    many-to-many relationship

    an entity of either set can be connected to many entities of the other set.

    many-to-one relationship

    each entity of the first set can be connected to at most one entity of the second set. and each entity of the second set can be connected to at least one entity of the first set.

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