Cardinality in an SQL database isn’t just a number representing rows in a table. It also has an impact on query performance. Learn how database cardinality works in this article. Cardinality is a term that originates from mathematics – more specifically, from relational algebra. But the term isn’t limited to the mathematical field; it also has implications in the world of databases. In this article, we will do a dive deep into this topic and explain cardinality in SQL databases and how it impacts your queries.
What is cardinality in data modeling? And how do you implement cardinality in databases? This discussion uses simple, easy-to-follow examples to describe both the theory and modeling of cardinality in ER diagrams. Cardinality is a mathematical term. It translates into the number of elements in a set. In databases, cardinality refers to the relationships between the data in two database tables. Cardinality defines how many instances of one entity are related to instances of another entity.