What is a one to one relationship in database?

One-to-One (1-1) relationship is defined as the relationship between two tables where both the tables should be associated with each other based on only one matching row. This relationship can be created using Primary key-Unique foreign key constraints.

In a one-to-one relationship, one record in a table is associated with one and only one record in another table.

For example:

In a school database, each student has only one student ID and each student ID is assigned to only one person.