How to Concatenate Multiple Values into a Comma-Separated String in MySQL?

Comma-Separated String of Selected Values in MySQL

Problem:

How can you convert selected values into a comma-separated string in MySQL? For instance, you have a query that returns multiple values, and you want to combine them into a single string.

Initial Code:

Here's an example query that selects several IDs from a table:

SELECT id
FROM table_level
WHERE parent_id = 4;

Desired Output:

Instead of separate rows, you wish to obtain a single string with all IDs comma-separated:

"5,6,9,10,12,14,15,17,18,779"

Solution:

The GROUP_CONCAT() function in MySQL is designed for this exact purpose. It concatenates multiple values into a single string, separated by a specified delimiter. Here's a revised query using GROUP_CONCAT():

SELECT GROUP_CONCAT(id)
FROM table_level
WHERE parent_id = 4
GROUP BY parent_id;

This query groups the results by parent_id and concatenates the ID values within each group, with a comma as the delimiter. The result will be a single row containing the desired comma-separated string of IDs.

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