mysql只选择唯一的行

Question

我想从表中选择唯一的唯一行，有人可以帮我吗？

SELECT * FROM table 
where to_user = ? 
and deleted != ? 
and del2 != ? 
and is_read = '0' 
    order by id desc 


+----+-----+------+ 
| id | message_id | 
+----+-----+------+ 
| 1 | 23   | 
| 2 | 23   | 
| 3 | 23   | 
| 4 | 24   | 
| 5 | 25   | 
+----+-----+------+ 

我需要这样的东西

+----+-----+------+ 
| id | message_id | 
+----+-----+------+ 
| 3 | 23   | 
| 4 | 24   | 
| 5 | 25   | 
+----+-----+------+ 

Answer 1

试试这个：

SELECT MAX(id), message_id 
FROM tablename 
GROUP BY message_id 

，如果您有其他的领域则：

SELECT MAX(id), message_id 
FROM tablename 
WHERE to_user = ? 
AND deleted != ? 
AND del2 != ? 
AND is_read = '0' 
GROUP BY message_id 
ORDER BY id DESC 

Answer 2

如果你只需要最大的ID对于特定的message_id

SELECT max(id), message_id FROM table 
where to_user = ? 
and deleted != ? 
and del2 != ? 
and is_read = '0' 
group by message_id 
    order by id desc 

Answer 3

尝试DISTINCT关键字。这将工作肯定：

SELECT DISTINCT(message_id), id FROM table;