How can I convert selected values into a comma-separated string in MySQL?

Comma-Separated String of Selected Values in MySQL

Converting selected values into a comma-separated string is a common task in MySQL. To achieve this, use the GROUP_CONCAT() function.

Consider the following example:

SQL

SELECT id
FROM table_level
WHERE parent_id = 4;

This query returns the following output:

MD

'5'
'6'
'9'
'10'
'12'
'14'
'15'
'17'
'18'
'779'

To display the selected values as a comma-separated string, use the following query:

SQL

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

This modified query results in the desired output:

MD

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

The GROUP_CONCAT() function aggregates the selected values, concatenates them with commas, and groups the result by the specified column (in this case, parent_id). By default, this function separates values with commas, but you can customize the separator using the SEPARATOR clause.

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