查询加入时最多

Question

如何获取maxMESSAGENUMBER？

mysql> 
mysql> describe ARTICLE;describeNEWSGROUP; 
+---------------+------------+------+-----+---------+----------------+ 
| Field   | Type  | Null | Key | Default | Extra   | 
+---------------+------------+------+-----+---------+----------------+ 
| ID   | bigint(20) | NO | PRI | NULL | auto_increment | 
| MESSAGENUMBER | int(11) | YES |  | NULL |    | 
| NEWSGROUP_ID | bigint(20) | YES | MUL | NULL |    | 
+---------------+------------+------+-----+---------+----------------+ 
3 rows in set (0.00 sec) 

+-----------+--------------+------+-----+---------+----------------+ 
| Field  | Type   | Null | Key | Default | Extra   | 
+-----------+--------------+------+-----+---------+----------------+ 
| ID  | bigint(20) | NO | PRI | NULL | auto_increment | 
| NEWSGROUP | varchar(255) | YES |  | NULL |    | 
+-----------+--------------+------+-----+---------+----------------+ 
2 rows in set (0.00 sec) 

mysql> 
mysql> select * from ARTICLE left join NEWSGROUP on ARTICLE.NEWSGROUP_ID=NEWSGROUP.ID where NEWSGROUP.newsgroup = "gwene.com.economist"; 
+----+---------------+--------------+------+---------------------+ 
| ID | MESSAGENUMBER | NEWSGROUP_ID | ID | NEWSGROUP   | 
+----+---------------+--------------+------+---------------------+ 
| 18 |    4 |   4 | 4 | gwene.com.economist | 
| 19 |    5 |   4 | 4 | gwene.com.economist | 
| 20 |    6 |   4 | 4 | gwene.com.economist | 
| 21 |    7 |   4 | 4 | gwene.com.economist | 
| 22 |    8 |   4 | 4 | gwene.com.economist | 
| 23 |    9 |   4 | 4 | gwene.com.economist | 
| 24 |   10 |   4 | 4 | gwene.com.economist | 
| 25 |   11 |   4 | 4 | gwene.com.economist | 
+----+---------------+--------------+------+---------------------+ 
8 rows in set (0.00 sec) 

mysql> 

Answer 1

SELECT MAX(MESSAGENUMBER) 
FROM ARTICLE left join NEWSGROUP on ARTICLE.NEWSGROUP_ID=NEWSGROUP.ID 
WHERE NEWSGROUP.newsgroup = "gwene.com.economist" 

Answer 2

select * from ARTICLE left join NEWSGROUP 
on ARTICLE.NEWSGROUP_ID=NEWSGROUP.ID 
where NEWSGROUP.newsgroup = "gwene.com.economist" 
ORDER BY MESSAGENUMBER DESC LIMIT 1