In database terminology, what describes the number of unique entries in a set of rows?

In database terminology, cardinality refers to the number of unique entries in a set of rows. When discussing a database, particularly when modeling relationships between tables, cardinality can represent the uniqueness of values in a column or the possible relationships between records in different tables. For example, in a table of customers, the cardinality of the "customer ID" column would indicate how many distinct customer IDs there are, reflecting the unique customers represented in that table.

The concept of cardinality is crucial in designing databases because it helps in understanding how entities relate to one another, which can influence database normalization and the overall structure of the schema. In relational databases, knowing the cardinality can assist in optimizing queries and improving performance.

The other terms could be confusing in this context. Multiplicity often pertains to the relationships between sets rather than the count of unique entries. Count is simply a numerical representation of all entries, not specific to uniqueness. Dimension typically refers to the attributes or characteristics of data within a database rather than quantifying unique rows. Thus, cardinality is the most appropriate term for describing the number of unique entries in a set of rows.