1

下面的查询被截断，“created”只显示“cre”（首先滚动到最右边:)：

 mysql> SELECT  GROUP_CONCAT(CONCAT('<comment><body><![CDATA[',body,']]></body>','<replier>',if(uid is not null,uid,''),'</replier>','<created>',created,'</created></comment>') SEPARATOR '')
        ->                                          FROM   idiscussion
        ->
        ->                                          WHERE  idiscussion.iask_id = 1;
    +------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
    | GROUP_CONCAT(CONCAT('<comment><body><![CDATA[',body,']]></body>','<replier>',if(uid is not null,uid,''),'</replier>','<created>',created,'</created></comment>') SEPARATOR '')                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
    +------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
    | <comment><body><![CDATA[haha]]></body><replier></replier><created>2009-05-27 04:57:51</created></comment><comment><body><![CDATA[haha]]></body><replier></replier><created>2009-05-27 04:57:52</created></comment><comment><body><![CDATA[haha]]></body><replier></replier><created>2009-05-27 04:57:52</created></comment><comment><body><![CDATA[haha]]></body><replier></replier><created>2009-05-27 04:57:53</created></comment><comment><body><![CDATA[r]]></body><replier></replier><created>2009-05-29 21:55:44</created></comment><comment><body><![CDATA[s]]></body><replier></replier><created>2009-05-29 23:04:39</created></comment><comment><body><![CDATA[dddret]]></body><replier></replier><created>2009-05-29 23:15:41</created></comment><comment><body><![CDATA[sser]]></body><replier></replier><created>2009-05-29 23:17:13</created></comment><comment><body><![CDATA[aaaaaaassaaaaaa]]></body><replier></replier><created>2009-05-29 23:23:32</created></comment><comment><body><![CDATA[testjjjjjjjjjjj]]></body><replier></replier><cre |
    +------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
    1 row in set, 1 warning (0.00 sec)

这是可数据结构和数据记录：

mysql> show create table idiscussion;
+-------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table       | Create Table                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
+-------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| idiscussion | CREATE TABLE `idiscussion` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `iask_id` int(10) unsigned DEFAULT NULL,
  `ianswer_id` int(10) unsigned DEFAULT NULL,
  `uid` int(10) unsigned DEFAULT NULL,
  `body` varchar(600) NOT NULL,
  `created` datetime NOT NULL,
  PRIMARY KEY (`id`),
  KEY `i_idiscussion_uid` (`uid`),
  KEY `i_idiscussion_iask` (`iask_id`),
  KEY `i_idiscussion_ianswer` (`ianswer_id`)
) ENGINE=InnoDB AUTO_INCREMENT=34 DEFAULT CHARSET=utf8 |
+-------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> select *from idiscussion;
+----+---------+------------+------+----------------------------+---------------------+
| id | iask_id | ianswer_id | uid  | body                       | created             |
+----+---------+------------+------+----------------------------+---------------------+
|  1 |       1 |       NULL | NULL | haha                       | 2009-05-27 04:57:51 |
|  2 |       1 |       NULL | NULL | haha                       | 2009-05-27 04:57:52 |
|  3 |       1 |       NULL | NULL | haha                       | 2009-05-27 04:57:52 |
|  4 |       1 |       NULL | NULL | haha                       | 2009-05-27 04:57:53 |
|  5 |    NULL |          1 | NULL | hey!                       | 2009-05-29 01:56:22 |
|  6 |    NULL |          1 | NULL | hey!                       | 2009-05-29 01:56:23 |
|  7 |    NULL |          1 | NULL | hey!                       | 2009-05-29 01:56:25 |
|  8 |    NULL |          2 | NULL | hey!                       | 2009-05-29 01:56:44 |
| 13 |    NULL |          1 | NULL | haha,works!                | 2009-05-29 21:29:50 |
| 14 |       1 |       NULL | NULL | r                          | 2009-05-29 21:55:44 |
| 15 |    NULL |          1 | NULL | so                         | 2009-05-29 21:55:57 |
| 16 |    NULL |          2 | NULL |                            | 2009-05-29 22:05:41 |
| 17 |    NULL |          3 | NULL | sss                        | 2009-05-29 22:16:27 |
| 18 |    NULL |          3 | NULL | hi                         | 2009-05-29 23:00:10 |
| 19 |    NULL |          1 | NULL | hi                         | 2009-05-29 23:03:06 |
| 20 |       1 |       NULL | NULL | s                          | 2009-05-29 23:04:39 |
| 21 |       1 |       NULL | NULL | dddret                     | 2009-05-29 23:15:41 |
| 22 |       1 |       NULL | NULL | sser                       | 2009-05-29 23:17:13 |
| 23 |       1 |       NULL | NULL | aaaaaaassaaaaaa            | 2009-05-29 23:23:32 |
| 24 |    NULL |          1 | NULL | aasasqwqwqw aa             | 2009-05-29 23:23:56 |
| 25 |    NULL |          6 | NULL | dianpinyixia...            | 2009-05-30 00:58:04 |
| 26 |       1 |       NULL | NULL | testjjjjjjjjjjj            | 2009-06-15 23:12:58 |
| 27 |       1 |       NULL | NULL | hhhhhhhhhhhhhhhhhhh        | 2009-06-15 23:14:08 |
| 28 |       1 |       NULL | NULL | hey..................      | 2009-06-15 23:18:47 |
| 29 |    NULL |          6 | NULL | kkkkkkkkkkkkkkkkkkkkk      | 2009-06-15 23:22:30 |
| 30 |    NULL |          6 | NULL | jjjjjjjjjjjjjjjjj          | 2009-06-15 23:24:58 |
| 31 |    NULL |          6 | NULL | ssssssssssssssssssssssssss | 2009-06-15 23:26:01 |
| 32 |       1 |       NULL | NULL | hahahahhaahhahahah         | 2009-06-15 23:26:30 |
| 33 |       1 |       NULL |    4 | .faint.................    | 2009-06-15 23:28:16 |
+----+---------+------------+------+----------------------------+---------------------+
29 rows in set (0.00 sec)
4

3 回答 3

3

这是一个配置设置：

group_concat_max_len=4096在我的.cnf

或者

SET GLOBAL group_concat_max_len=4096
于 2009-06-15T15:57:35.207 回答
2

从文档：

结果被截断为系统变量给出的最大长度，group_concat_max_len其默认值为1024. 该值可以设置得更高，尽管返回值的有效最大长度受 值的限制max_allowed_packet。在运行时更改 的值的语法group_concat_max_len如下，其中val 是一个无符号整数：

 SET [GLOBAL | SESSION] group_concat_max_len = val;
于 2009-06-15T15:57:48.343 回答
1

从文档：

结果被截断为 group_concat_max_len 系统变量给出的最大长度，默认值为 1024。

您的截断字符串自然有 1024 个字符长。

于 2009-06-15T15:58:52.447 回答