How to Maintain Referential Integrity in Exclusive and Non-Exclusive Subtype Database Implementations?

Referential Integrity in Subtype Implementations

Introduction

Referential integrity in subtype structures ensures that there is a valid relationship between parent and child tables. Exclusive subtypes allow only one subtype for a given parent, while non-exclusive subtypes allow multiple subtypes.

Exclusive Subtypes

To implement referential integrity for exclusive subtypes:

1. Discriminator Column: Add a discriminator column to the parent table to indicate the subtype.

   • Implement a CHECK CONSTRAINT to ensure the discriminator value is within the allowed range.
2. Primary Key to Foreign Key Relationship: The primary key of the parent table becomes the foreign key in the subtype table, ensuring a single subtype per parent row.
3. User-Defined Function (UDF): Create a UDF that checks if the primary key and discriminator exist in the parent table.
4. CHECK CONSTRAINT in Subtype Table: Implement a CHECK CONSTRAINT in the subtype table to call the UDF and validate the parent existence.
5. Transaction Checks: Use transactional logic to verify that at least one subtype exists for each parent.

Non-Exclusive Subtypes

For non-exclusive subtypes:

1. Primary Key to Foreign Key Relationship: Establish a primary key to foreign key relationship as in exclusive subtypes.
2. Existence Check: Perform an existence check on the subtype table using the parent primary key to determine whether a subtype exists or not.

Advantages of UDF-Based Approach

• Avoids data duplication and indices overkill.
• Handles scenarios where the subtype is not present at the time of parent insert.

Response to Comments

• Update Protection for Discriminator: Open Architecture Standards (ACID Transactions) prevent unauthorized updates. Additionally, controlled access to the database and use of Transactions ensure that updates preserve data integrity.
• UDF vs. Duplicate Discriminator FK: UDFs provide a more efficient and flexible solution without the need for additional tables and indices.

The above is the detailed content of How to Maintain Referential Integrity in Exclusive and Non-Exclusive Subtype Database Implementations?. For more information, please follow other related articles on the PHP Chinese website!