Entity-Relationship (ER) Diagrams
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Close up on participation constraints:
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Ternary relationship:

AdvisedBy(StudentRIN, MajorCode, FacultyRIN)

Key: StudentRIN, MajorCode

Students Major -> Faculty


Binary Model:

R1(StudentRIN, MajorCode)
R2(StudentRIN, FacultyRIN)
R3(FacultyRIN, MajorCode)

Decomposition!

 S    F    M
 s    f1   m
 s    f    m2
 s3   f    m

Cannot apply s m -> f

Lossy decomposition: representing ternary relationship in three binary
relationship does not give me the same exact result!

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Alternate model:

Ternary relationship:

AdvisedBy(StudentRIN, MajorCode, FacultyRIN)

Keys: StudentRIN MajorCode, StudentRIN FacultyRIN


Students Major -> Faculty
Faculty -> Major

Binary Model:

R1(StudentRIN, MajorCode)
R2(StudentRIN, FacultyRIN)
R3(FacultyRIN, MajorCode)

Decomposition!

 S    F    M
 s    f1   m
 s    f    m2
 s3   f    m

f -> m

 S    F    M
 s    f    m   <-- lossless decomposition
 s    f    m2
 s3   f    m