In a database management system (DBMS), what is the “cardinality?”
A.
The number of rows in a relation.
B.
The number of columns in a relation.
C.
The set of allowable values that an attribute can take.
D.
The number of relations in a database.
Explanation:
In database design, the cardinality or fundamental principle of one data table with respect to another is a critical
aspect. The relationship of one to the other must be precise and exact between each other in order to explain
how each table links together.
In the relational model, tables can be related as any of “one-to-many” or “many-to-many.” This is said to be the
cardinality of a given table in relation to another.
Incorrect Answers:
B: The number of columns in a relation would be the size of the key. It is not the cardinality of the relation.
C: Cardinality concerns the relation between two tables, not allowable attributes.
D: Cardinality concerns one specific relation between two tables, not the number of relations in a database.https://en.wikipedia.org/wiki/Cardinality_(data_modeling)
In the context of databases, cardinality refers to the uniqueness of data values contained in a column. High cardinality means that the column contains a large percentage of totally unique values. Low cardinality means that the column contains a lot of “repeats” in its data range.
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