MySQL Configuration and tuning Increase the string limit for group_concat
Example
group_concat is used to concatenate non-null values in a group. The maximum length of the resulting string can be set using the group_concat_max_len option:
SET [GLOBAL | SESSION] group_concat_max_len = val;
Setting the GLOBAL variable will ensure a permanent change, whereas setting the SESSION variable will set the value for the current session.
