A one-to-many relationship exists in a database when each record in Table A can have multiple linked records in Table B, but each record in Table B can have only one corresponding record in Table A.
SQL Server Tutorial – One-to-many and many-to-many table relationships
A one-to-many relationship in a database is the most common relational database design and is at the heart of good design.
Consider the relationship between a teacher and the courses he/she teaches. A teacher may teach multiple classes, but the course would not have the same relationship with the teacher.
Therefore, for every record in a Teachers table, there can be many records in the Courses table. This example illustrates a one-to-many relationship: one teacher to many courses.
