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Relationships among FDs and ERDs.

Relationships among FDs and ERDs. In the previous lectures, we saw that a schema that can be generated from a mapped translation satisfies 3NF. In reverse direction, we can generate all FDs from an ERD. We discuss these FDs from Intra FDs and Inter FDs. Cont’. (1) Intra FDs:

phailin-suttikul
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Relationships among FDs and ERDs.

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  1. Relationships among FDs and ERDs. In the previous lectures, we saw that a schema that can be generated from a mapped translation satisfies 3NF. In reverse direction, we can generate all FDs from an ERD. We discuss these FDs from Intra FDs and Inter FDs.

  2. Cont’ (1) Intra FDs: - The identifier of an entity determines all non-key attributes. (2) Inter FDs

  3. Inter FDs Suppose we have a relationship R between entity A and entity B, where whose primary keys are A# and B#. Then, we have the following FDs between two entities, depending on cardinality: (a) 1:1 A# --> B# B# --> A# (b) 1:N B# --> A# (note: A# -/-> B#)

  4. Inter FDs (c) M:N no FDs between A# and B# (note: A# -/-> B# and B# -/-> A# ) Suppose relationship R has an attribute called W. Then, we have: A#B# --> W

  5. Cont’

  6. Intra FDs Pic# -->PicTitle, PicYear PicArtist -->ArtistCountry, ArtistType Museum# -->MuseumName, MuseumAddr

  7. Inter FDs Pic# -->PicArtist, Museum#

  8. Cont’ Thus, we can combine them based on their common LHS. Pic# -->PicTitle, PicYear, PicArtist, Museum# PicArtist -->ArtistCountry, ArtistType Museum# -->MuseumName, MuseumAddr

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