我从mysql查询结果中得到不完整的字符串值。当字符串太长时，该值将被切片。我把这个值作为 JSON 字符串。无论字段值有多长，我的本地数据库都没有问题。
我的问题是：

CREATE DEFINER=`devdbuser`@`localhost` PROCEDURE `GetTrainingFilesByID`(IN trainingID int)
BEGIN  
  SELECT t1.*, concat(t2.firstname,' ',t2.lastname) as username
  FROM users t2
  INNER JOIN 
  (
    SELECT t.*,
    CONCAT('[',
          GROUP_CONCAT(CONCAT('{"id":"',d.id,
                               '","name":"', d.title, 
                               '","file_path":"',d.doc_path,
                               '","is_video":"',d.is_video,'"}'
                              )), ']'
          ) files 
          FROM training t 
          LEFT JOIN training_documents d 
          ON t.id = d.training_id 
          GROUP BY t.id
  ) t1
  ON t1.updated_by = t2.id
  WHERE t1.id = trainingID
  LIMIT 1;
  END

问题在于 files 字段值。
这是你的答案 incomplete 输出：

"[{"id":"1", "name":"Branch Workflow Model for GBD_1.pdf", "file_path":"1455443689.pdf", "is_video":"0"},
  {"id":"2", "name":"http://192.168.11.32/GBD-Videos/testvideo.mp4", "file_path":"http://192.168.11.32/GBD-Videos/testvideo.mp4", "is_video":"1"},
  {"id":"6", "name":"COD-CC-CrowdWisdom-Report-exclusive_mybigcommerce_com-2018_09_26-05_28_58.pdf", "file_path":"1862665875.pdf", "is_video":"0"},
  {"id":"7", "name":"https://www.youtube.com/watch?v=rCAIY5n1hPA.mp4", "file_path":"https://www.youtube.com/watch?v=rCAIY5n1hPA.mp4", "is_video":"1"},
  {"id":"8", "name":"https://www.youtube.com/watch?v=rCAIY5n1hP1.mp4", "file_path":"https://www.youtube.com/watch?v=rCAIY5n1hP1.mp4", "is_video":"1"},
  {"id":"19", "name":"Branch Workflow Model for GBD.docx", "file_path":"1250685453.docx", "is_video":"0"},
  {"id":"20", "name":"COK_CorporateMedicineDelivery_Growbydata.pdf", "file_path":"1245383653.pdf", "is_video":"0"},
  {"id":"21", "name":"COK_Intro_Growbydata.pdf", "file_path":"1918218679.pdf", "is_video":"0"},
  {"id":"22", "name":"http:/]"

mysql是否有防止长字段结果值的功能？我该怎么解决这个问题？