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Databases & SQL vocabulary · Data Modeling and Normalization

One-to-many relationship

Meaning in databases & SQL, with examples

nounCore term

In databases & SQL, one-to-many relationship means: A link between two tables where one row in the first table can be connected to many rows in the second, but each of those belongs to only one, like a customer and their orders.

In Turkish: bire-çok ilişki, bir-çok ilişkisi

How it is used

The most common relationship in databases. It is built with a foreign key on the 'many' side, for example customer_id in the orders table. Also written 1:N or 1-to-many. ORMs describe the two sides as 'has many' and 'belongs to'.

Example sentences

  1. There is a one-to-many relationship between departments and employees.

  2. To model a one-to-many relationship, put the foreign key on the child table.

Common collocations

  • one-to-many relationship between
  • 1:N relationship
  • parent and child tables
  • has many
  • many-to-many relationshipA link where many rows in one table can relate to many rows in another, like students and courses. It needs a third table in between to store the pairs.
  • foreign keyA column in one table that points to the primary key of another table, linking the two and stopping you from storing references to rows that do not exist.
  • ER diagramA drawing of a database design that shows the entities (usually tables), their attributes and the relationships between them, such as one-to-many.
  • cardinalityEither the type of relationship between tables (one-to-one, one-to-many, many-to-many) or the number of distinct values in a column.

This word in other fields

The same English word can have a different meaning in another field:

More terms: Data Modeling and Normalization

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