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chem1111 chem1111
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6 years ago
What is a foreign key? Why are foreign keys used or required in a relational database? Are duplicate foreign key values allowed? Why or why not?
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6 years ago
A foreign key is a field value (or set of values) stored in one table that also exists as a primary key value in another table. Foreign keys are used to represent relationships among entities that are represented as tables. Duplicate foreign keys are not allowed within the same table because they would redundantly represent the same relationship. Duplicate foreign keys may exist in different tables because they would represent different relationships.
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