Many-to-One and One-to-Many
Many-to-One and One-to-Many are essentially inverse perspectives of the same relational concept, especially in the context of databases.
Many-to-One
From the perspective of the "many" side, a record can have a relationship to one record in another table. This is essentially a straightforward foreign key relationship. In a many-to-one connection, numerous records from one table can correspond to a single record in another table. It's the most common type of relationship in relational databases.
![](https://codefinity-content-media-v2.s3.eu-west-1.amazonaws.com/courses/5ac24d9d-4a16-45b3-8856-07dec028c5e9/Section+2/M-O_std-schl%404x-8.png)
For instance, every Student has a reference to a School, indicated by the school_id.
One-to-Many
This is a relationship where a single record from one table can link to multiple records in another table. This particular table has a list of primary keys serving as a singular foreign key. Such a relationship is uncommon in relational databases and doesn't establish robust dependencies. Therefore, it's generally considered a poor practice in the context of relational databases, though it may find use in non-relational databases.
![](https://codefinity-content-media-v2.s3.eu-west-1.amazonaws.com/courses/5ac24d9d-4a16-45b3-8856-07dec028c5e9/Section+2/O-M_schl-std%404x-8.png)
Everything was clear?
Course Content
Relational Database and Normalization
3. Normalization and Normal Forms
Relational Database and Normalization
Many-to-One and One-to-Many
Many-to-One and One-to-Many are essentially inverse perspectives of the same relational concept, especially in the context of databases.
Many-to-One
From the perspective of the "many" side, a record can have a relationship to one record in another table. This is essentially a straightforward foreign key relationship. In a many-to-one connection, numerous records from one table can correspond to a single record in another table. It's the most common type of relationship in relational databases.
![](https://codefinity-content-media-v2.s3.eu-west-1.amazonaws.com/courses/5ac24d9d-4a16-45b3-8856-07dec028c5e9/Section+2/M-O_std-schl%404x-8.png)
For instance, every Student has a reference to a School, indicated by the school_id.
One-to-Many
This is a relationship where a single record from one table can link to multiple records in another table. This particular table has a list of primary keys serving as a singular foreign key. Such a relationship is uncommon in relational databases and doesn't establish robust dependencies. Therefore, it's generally considered a poor practice in the context of relational databases, though it may find use in non-relational databases.
![](https://codefinity-content-media-v2.s3.eu-west-1.amazonaws.com/courses/5ac24d9d-4a16-45b3-8856-07dec028c5e9/Section+2/O-M_schl-std%404x-8.png)
Everything was clear?