How to Effectively Store Lists of Values in a Relational Database?

Storing Lists in Database Columns: Relational Database Approach

When faced with the task of storing a list of values within a database column, it's crucial to consider the constraints of a normalized relational database.

A simple list, such as the one described in the question, introduces anomalies and data redundancy in a relational system. To address this, it's recommended to establish a junction table.

Junction Table Approach

A junction table connects two existing tables by creating a new table that consists of a column for each table's unique identifier (ID) and a primary key tuple that uniquely identifies each row. This approach allows for the inclusion of a referenced field from the list table and the establishment of a many-to-many relationship between the two tables.

For instance, in the FOO object example:

1. Create the FOO table with columns for the three integers and a surrogate key.
2. Create the Fruits table with columns for the fruit names and a surrogate key.
3. Create the FOOFruits junction table with columns for the FruitID and FooID, forming the primary key.

Example Query

To add Apple to the fruit list for FOO object with ID 5:

INSERT INTO FOOFruits (FooID, FruitID)
SELECT 5, ID FROM Fruits WHERE name = 'Apple'

This query selects the FruitID and FooID from the Fruits table where the name is 'Apple' and inserts them into the FOOFruits table, establishing the relationship between the FOO object and the Apple fruit.

By adhering to this approach, you can effectively store list data in a relational database while maintaining data integrity and avoiding anomalies, ensuring the accuracy and consistency of your data over time.

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