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.