Understanding Database Cardinality

A Guide to Key Relationships and Data Uniqueness in Databases

Database cardinality is a fundamental concept in the realm of database design and management. It refers to the uniqueness of data values contained in a particular column (attribute) of a database table. Cardinality plays a crucial role in determining the relationships between tables and how efficiently a database can handle queries.

Types of Cardinality

There are several types of cardinality in databases, primarily focusing on the relationships between tables and the distinctiveness of data within columns.

One-to-One (1:1) Cardinality

In a one-to-one relationship, a single row in one table is associated with a single row in another table. This type of relationship is less common and is typically used when data can be logically divided into two tables but still maintains a direct relationship.

Example:

Users Table: Contains user-specific information like user ID and username.

UserProfiles Table: Contains profile details like bio and profile picture URL.

Each user in the Users table has exactly one corresponding profile in the UserProfiles table.