In systems analysis, a one-to-many relationship is a type of cardinality that refers to the relationship between two entities (see also entity–relationship model).
In a relational database, a one-to-many relationship exists when one record is related to many records of another table.
This is also called a foreign key constraint, which is important to keep data from being duplicated and have relationships within the database stay reliable as more information is added.
Both one-to-many and one-to-one relationships are common in relational databases but are normally created majorly with one-to-many relationships.
One notation as described in Entity Relationship modeling is Chen notation or formally Chen ERD notation created originally by Peter Chen in 1976 where a one-to-many relationship is notated as 1:N where N represents the cardinality and can be 0 or higher.