Mysql group_concat () function traps

Mysql group_concat () function traps my colleague sent me a rest interface today saying there should be data, but no data was found. Solution: After troubleshooting, we found that mysql's group_concat () function only returns a 1024-length string by default, and the output variable defined in my stored procedure is out board_list VARCHAR (4000 ), www.2cto.com. The maximum returned value of this stored procedure is 100000 characters. when group_concat_max_len = 200000 is added to ini, the output variable definition is changed to out board_list VARCHAR (200000) to solve the problem. Author: sdu_wizard