What is the definition of cardinality in the context of a relational database?

Cardinality in the context of a relational database refers to the number of rows in a table. It indicates how many records or instances are present in that table, which is a key aspect of database design and optimization. Understanding cardinality is crucial for various database operations, including indexing and join operations, as it impacts performance and query planning. Higher cardinality means more rows, which can affect how data is accessed, retrieved, and processed by the database management system.

The other choices refer to different database concepts unrelated to cardinality. For instance, the number of attributes relates to the table's structure and its fields, while the number of tables addresses the overall schema rather than individual data instances. The number of columns, similar to attributes, pertains to the specific data organization within a table rather than the count of records. Thus, recognizing that cardinality specifically deals with the count of rows is essential for understanding relational database characteristics.