How to adjust the group_concat_max_len parameter in MySQL?

To adjust the group_concat_max_len parameter in MySQL, you can modify it either dynamically for the current session or permanently by updating the configuration file.

1. Dynamic Adjustment (Session-Level):
   Use the SET statement to change the value for the current session. This change only affects the current connection and resets after the session ends.
   Example:

   SET SESSION group_concat_max_len = 1000000;
   

   To apply it globally for all new sessions (but requires SUPER privilege):

   SET GLOBAL group_concat_max_len = 1000000;
   

2. Permanent Adjustment (Configuration File):
   Edit the MySQL configuration file (my.cnf or my.ini depending on the OS) and add or update the parameter under the [mysqld] section.
   Example:

   [mysqld]
   group_concat_max_len = 1000000
   

   After saving the file, restart the MySQL service to apply the changes.

If you're using Tencent Cloud Database MySQL, you can adjust this parameter via the Tencent Cloud Console:

• Navigate to the Database Management page.
• Select your MySQL instance and go to Parameters.
• Search for group_concat_max_len, modify its value, and save. The change may require a restart of the instance.

For temporary adjustments in Tencent Cloud, use the SET command as shown above.