How to Model One-to-One Relationships Between Multiple Tables in a Database?

How to Model One-to-One Relationships between Multiple Tables

Problem:

In a database schema, you have a storage table that serves as a join point for van and warehouse tables, with each storage entity being associated with only one storage location type. However, you're unsure of the optimal way to establish these one-to-one relationships.

Answer:

The database modeling technique known as inheritance (or "subclass" or "category") offers three approaches to represent one-to-one relationships:

1. All classes in one table:
   A single table combines both the parent and all child classes, enforcing constraints to ensure the proper subset of fields is not NULL (i.e., different children do not mix).
2. Concrete class per table:
   Separate tables exist for each child, but there is no parent table. Parent relationships are duplicated in all children.
3. Class per table:
   A parent table and a dedicated table for each child. This option provides the cleanest representation but may incur performance costs for data modifications.

For your specific scenario, it's recommended to use the third approach, "Class per table." However, to ensure both the presence and exclusivity of a child, consider implementing these constraints at the application level. While enforcing both at the database level can be cumbersome, it's possible with deferred constraints. If your DBMS does not support them, you can create exclusive relationships using type discriminators and computed columns.

The above is the detailed content of How to Model One-to-One Relationships Between Multiple Tables in a Database?. For more information, please follow other related articles on the PHP Chinese website!