What is cardinality in SQL?

In SQL, Cardinality is the uniqueness of data values in a column. If cardinality is low then a column will have more duplicated values.

Database use Cardinality of a column to determine the optimal query plan for a query.

of elements in a set. Thinking in the database world, cardinality has to do with the counts in a relationship, one-to-one, one-to-many, or many-to-many.

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