mysql 5.6 通过 sql 获取字符串 json key

CREATE  FUNCTION `fn_Json_getKeyValue`(
 in_JsonArray MEDIUMTEXT,# JSON数组字符串
 in_Index TINYINT,       # 从json 对象序号,序号从1开始
 in_KeyName VARCHAR(512) # 键名
) RETURNS varchar(2048) CHARSET utf8
BEGIN
    # 定义参数
    DECLARE vs_Return VARCHAR(4096);
    DECLARE vs_JsonArray, vs_Json, vs_KeyName VARCHAR(4096);
    DECLARE vi_Pos1,vi_Pos2 SMALLINT UNSIGNED;
    
    # 写入监控日志 暂不记录
    
    SET vs_JsonArray = TRIM(in_JsonArray);
    SET vs_KeyName = TRIM(in_KeyName);

    IF vs_JsonArray = '' OR vs_JsonArray IS NULL
         OR vs_KeyName = '' OR vs_KeyName IS NULL
         OR in_Index <= 0 OR in_Index IS NULL THEN
         SET vs_Return = NULL;
    ELSE
         SET vs_JsonArray = REPLACE(REPLACE(vs_JsonArray, '[', ''), ']', '');
         # 取指定json 对象
         SET vs_Json = SUBSTRING_INDEX(SUBSTRING_INDEX(vs_JsonArray,'}', in_index),'}',-1);
         IF vs_Json = '' OR vs_json IS NULL THEN
                SET vs_Return = NULL;
         ELSE
              SET vs_KeyName = CONCAT('"',vs_KeyName,'":');
                SET vi_Pos1 = INSTR(vs_Json,vs_KeyName);
                IF vi_Pos1 > 0 THEN
                    # 键名不存在
                    SET vi_Pos1 = vi_Pos1 + CHAR_LENGTH(vs_KeyName);
                    SET vi_Pos2 = LOCATE(',',vs_Json,vi_Pos1);
                    IF vi_Pos2 = 0 THEN
                         SET vi_Pos2 = CHAR_LENGTH(vs_Json) + 1;
                    END IF;
                    SET vs_Return = REPLACE(MID(vs_Json,vi_Pos1,vi_Pos2-vi_Pos1),"",'');
                END IF;
     END IF;
  END IF;
    RETURN vs_Return;
END