How can you use GROUP_CONCAT() function in SQL?

The GROUP_CONCAT() function in SQL is used to combine multiple row values into a single string — it’s especially useful when you want to display related values in one line instead of multiple rows.

For example, if I have a table called Students and I want to list all student names grouped by their class, I can write:

SELECT Class, GROUP_CONCAT(StudentName) AS Students
FROM Students
GROUP BY Class;

If the Students table has this data:

The output will be:

So, GROUP_CONCAT() takes all the student names from the same class and joins them into a single comma-separated string.

In one of my reporting projects, I used GROUP_CONCAT() to display all product names purchased in each order on a single line instead of showing multiple rows per order. It made the summary report much easier to read.

You can also customize the separator using the SEPARATOR keyword. For example:

SELECT Class, GROUP_CONCAT(StudentName SEPARATOR ' | ') AS Students
FROM Students
GROUP BY Class;

This will separate names with a “|” symbol instead of a comma.

A few things to note:

• GROUP_CONCAT() is available in MySQL and SQLite, but in other databases like SQL Server, you use STRING_AGG() instead.
• There’s a length limit on the concatenated string (group_concat_max_len in MySQL), so for very large text results, you may need to increase that setting.

So, in short — GROUP_CONCAT() helps you combine multiple values from grouped rows into a single text field, making it great for summary or display-oriented queries.