Efficient Search for Comma-Separated Values in MySQL Database

When working with data tables that contain comma-separated values, finding specific matches can be a challenging task. In this case, you have two tables: customers (containing email addresses) and imap_emails (where the to field holds comma-separated email addresses). You need to efficiently search within the imap_emails table based on email addresses from the customers table.

Instead of using a LIKE condition, you can leverage the FIND_IN_SET function to perform a more targeted search. This function allows you to check if a specific value is found within a comma-separated string.

Solution:

The following query demonstrates how you can use FIND_IN_SET for efficient searching:

SELECT *
FROM imap_emails
INNER JOIN customers
ON FIND_IN_SET(customers.email, imap_emails.to) > 0

This query performs an inner join between the two tables, matching rows where the customer's email is present in the comma-separated to field of the imap_emails table. By using FIND_IN_SET instead of LIKE, you improve the search efficiency and avoid false positives.

Additional Considerations:

In your question, you mentioned that you cannot use relationships between the tables. However, if you have the ability to establish a relationship (e.g., using foreign keys), it would significantly enhance the data integrity and performance of your search queries.