跪求一句SQL语句，坐等。解决办法

跪求一句SQL语句，坐等。
4个表，

box是盒子，
note是消息，
box_user是哪些用户在哪些盒子里聊天。
box_note是哪些消息在哪些盒子里（消息可在多盒共享）。

盒子就和微信的一个聊天框一样，消息就是里面的消息。

SQL code

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mysql> describe box;      
+---------------------------+------------+------+-----+---------+----------------+
| Field                     | Type       | Null | Key | Default | Extra          |
+---------------------------+------------+------+-----+---------+----------------+
| box_id                    | bigint(20) | NO   | PRI | NULL    | auto_increment |
| type                      | tinyint(4) | NO   |     | NULL    |                |
| status_type               | char(1)    | NO   |     | NULL    |                |
| create_time               | datetime   | NO   |     | NULL    |                |
| delete_time_from_one_part | datetime   | NO   |     | NULL    |                |
+---------------------------+------------+------+-----+---------+----------------+
5 rows in set (0.00 sec)

mysql> describe box_user;
+---------+------------+------+-----+---------+-------+
| Field   | Type       | Null | Key | Default | Extra |
+---------+------------+------+-----+---------+-------+
| user_id | bigint(20) | NO   | PRI | 0       |       |
| box_id  | bigint(20) | NO   | PRI | 0       |       |
+---------+------------+------+-----+---------+-------+
2 rows in set (0.01 sec)

mysql> describe note;
+-------------+-------------+------+-----+---------+----------------+
| Field       | Type        | Null | Key | Default | Extra          |
+-------------+-------------+------+-----+---------+----------------+
| note_id     | bigint(20)  | NO   | PRI | NULL    | auto_increment |
| user_id     | bigint(20)  | NO   | MUL | NULL    |                |
| type        | tinyint(4)  | NO   |     | NULL    |                |
| content     | text        | NO   |     | NULL    |                |
| mood        | tinyint(4)  | NO   |     | NULL    |                |
| locate      | varchar(30) | NO   |     | none    |                |
| privacy     | char(1)     | NO   |     | 1       |                |
| create_time | datetime    | NO   | MUL | NULL    |                |
| delay       | int(11)     | NO   |     | 0       |                |
| festival    | char(30)    | NO   |     | NULL    |                |
| delete_time | datetime    | NO   |     | NULL    |                |
+-------------+-------------+------+-----+---------+----------------+
11 rows in set (0.00 sec)

mysql> describe box_note;
+---------+------------+------+-----+---------+-------+
| Field   | Type       | Null | Key | Default | Extra |
+---------+------------+------+-----+---------+-------+
| note_id | bigint(20) | NO   | PRI | 0       |       |
| box_id  | bigint(20) | NO   | PRI | 0       |       |
+---------+------------+------+-----+---------+-------+
2 rows in set (0.00 sec)

想法很简单，试了半天都失败：想根据user_id获取该user的所有盒子以及每个盒子最后一条消息的时间。

我准备了这两个基本SQL语句，

SQL code

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//获取所有user_id用户的盒子
select box.box_id,type,status_type from box,box_user where box.box_id=box_user.box_id and box_user.user_id=1;
//获取所有内部具有消息的user_id用户的盒子以及最后更新时间
select box_id,max(create_time) as time from note,box_note where note.note_id=box_note.note_id and note.user_id=1 group by box_id;

它们分别执行结果：

SQL code

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-->mysql> select box.box_id,type,status_type from box,box_user where box.box_id=box_user.box_id and box_user.user_id=1;
+--------+------+-------------+
| box_id | type | status_type |
+--------+------+-------------+
|      1 |    0 | 0           |
|      6 |    1 | 0           |
|      7 |    3 | 0           |
|      8 |    3 | 0           |
+--------+------+-------------+
4 rows in set (0.00 sec)

mysql> select box_id,max(create_time) as time from note,box_note where note.note_id=box_note.note_id and note.user_id=1 group by box_id;
+--------+---------------------+
| box_id | time                |
+--------+---------------------+
|      1 | 2012-05-21 00:00:00 |
|      6 | 2012-05-30 00:00:00 |
+--------+---------------------+
2 rows in set (0.00 sec)


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