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Posts: 188
4 months ago
What is meant by the cardinality of a relationship?
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Database Processing: Fundamentals, Design, and Implementation
Edition: 15th
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4 months ago
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In the E-R model, there are two types of cardinality–the maximum cardinality and the minimum cardinality. The maximum cardinality is the maximum number of entity instances that can participate in a relationship instance. There are three types of maximum cardinality: one-to-one (1:1), one-to-many (1:N) and many-to-many (N:M). The minimum cardinality is the minimum number of entity instances that must participate in a relationship instance. This number is generally zero (0) or one (1). If the number is zero, then participation by that entity instance is optional (O)–it does not have to be in a relationship with an instance of the other entity. If the number is one, then participation by that entity instance is mandatory (M)–it must participate in a relationship with an instance of the other entity. In a binary relationship there are four (4) possible sets of minimum cardinalities–(O-O), (O-M), (M-O) and (M-M).
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4 months ago
This helped my grade so much
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4 months ago
Perfect
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