Consider a relation involving suppliers, parts, and projects:Initial Table (SupplierPartsProjects)Supplier Part Project S1 P1 J1S1 P2 J1S1 P1 J2S2 P2 J2Assume the following constraints:i. Every part supplied for a project is supplied by all suppliers supplying any part for that project.ii. Every part supplied by a supplier is supplied by that supplier for all projects to which that supplier supplies any part.In the given example, what join dependencies exist on the table "SupplierPartsProjects"?
Question
Consider a relation involving suppliers, parts, and projects:Initial Table (SupplierPartsProjects)Supplier Part Project S1 P1 J1S1 P2 J1S1 P1 J2S2 P2 J2Assume the following constraints:i. Every part supplied for a project is supplied by all suppliers supplying any part for that project.ii. Every part supplied by a supplier is supplied by that supplier for all projects to which that supplier supplies any part.In the given example, what join dependencies exist on the table "SupplierPartsProjects"?
Solution
The join dependencies in the "SupplierPartsProjects" table are based on the constraints provided.
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The first constraint states that every part supplied for a project is supplied by all suppliers supplying any part for that project. This implies a join dependency between Supplier, Part, and Project. In other words, the table "SupplierPartsProjects" can be decomposed into two tables: "SupplierProject" and "ProjectPart", and can be perfectly reconstructed by taking the natural join of these two tables.
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The second constraint states that every part supplied by a supplier is supplied by that supplier for all projects to which that supplier supplies any part. This implies another join dependency between Supplier, Part, and Project. In this case, the table "SupplierPartsProjects" can be decomposed into two tables: "SupplierPart" and "SupplierProject", and can be perfectly reconstructed by taking the natural join of these two tables.
So, the join dependencies for the "SupplierPartsProjects" table are {Supplier, Project} JOIN {Project, Part} and {Supplier, Part} JOIN {Supplier, Project}.
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