How Can I Efficiently Retrieve Usernames from a Comma-Separated Column in a Database?

Extracting Usernames from Comma-Separated Column

Consider a scenario where you have multiple tables: tblA (users), tblB (usernames), and tblC (nomenclature with comma-separated user IDs). The goal is to retrieve all usernames when searching for a specific nomenclature value.

Existing Approach and Limitations

The provided query attempts to use a cross join and a substring function to extract the first userID from the comma-separated value. However, this approach is inefficient and does not provide accurate results when there are multiple user IDs associated with the nomenclature.

Normalized Schema and Improved Query

It is recommended to normalize the database schema by introducing a junction table. The tblC_user table should contain two columns: c_id (referencing tblC) and userID (referencing tblB). This will eliminate the need for comma-separated user IDs in tblC.

The following query demonstrates how to extract usernames using the normalized schema:

SELECT *
FROM tblC c
JOIN tblC_user cu ON (c.id = cu.c_id)
JOIN tblB b ON (b.userid = cu.userid)
WHERE c.nname = "new1";

This query will efficiently retrieve all usernames associated with the "new1" nomenclature.

Benefits of Normalization

Normalizing the database schema offers several advantages:

• Improved data integrity and accuracy
• Faster queries and reduced processing time
• Simplified data maintenance and modification
• Cascading relations for maintaining child records

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