# Mysql: Bug fixing - GROUP_CONCAT

## Problem
GROUP_CONCAT can not get complete data from DB

## Reason
Default limit length of GROUP_CONCAT: 1024

## Solution
1. SET SESSION group_concat_max_len=102400; SET GLOBAL group_concat_max_len=102400;

* SET SESSION: this setting will work immediately, but affect only for current session.
* SET GLOBAL: this setting will work after restarting the Mysql server.
* Checking: SHOW VARIABLES LIKE '%group_concat%';

So, we should use them together.

**Attention:** the upper limit of max_length depends on the parameter "max_allowed_packet"

**To check:** SHOW VARIABLES LIKE '%max_allowed_packet%';

2. Change the my.cnf config file.

* find the file in /etc/my.cnf(Address different possible)
* increase the **group_concat_max_len = 102400**
* Checking: SHOW VARIABLES LIKE '%group_concat%';