In database terminology, what does data cardinality refer to?

In database terminology, what does data cardinality refer to?

• A. The total number of entities in a database
• B. The frequency of one item in relation to another
• C. The types of relationships between data tables
• D. The size of the database on disk

Answer: (B)

Data cardinality refers to the frequency of one item in relation to another. This concept is crucial in understanding the relationships and constraints that exist within a database. In relational database design, cardinality helps define how many instances of one entity relate to instances of another entity. For example, in a one-to-many relationship, one record in the first table can relate to many records in the second table, while each of those records in the second table relates back to just one record in the first table.

Understanding cardinality is essential for database normalization, which aims to reduce data redundancy and improve data integrity. It provides insights into how data entities share relationships, which influences the overall structure and queries executed within the database.

The other options touch on different aspects of databases but do not describe cardinality accurately. The total number of entities in a database pertains to data volume rather than relationships. The types of relationships between data tables previously mentioned fall under relationship types, such as one-to-one or one-to-many, rather than cardinality itself. The size of the database on disk is a measure of storage consumption, not a characterization of data relationships.