MySQL的左连接一个表与自身

Question

请考虑下面的表 '嗯'：

select * from mmm; 

输出：

+-------+-------+------+ 
| texto | value | n | 
+-------+-------+------+ 
| aaa | 10 | 1 | 
| aab | 10 | 1 | 
| aaa | 11 | 1 | 
| aab | 11 | 1 | 
| aaa | 10 | 2 | 
+-------+-------+------+ 

命令：

select a.*, '--', b.* 
    from mmm a 
left join mmm b on (a.n=b.n) 
where a.value < b.value 
    and a.texto ='aaa' 
    and b.texto='aab'; 

回报：

+-------+-------+------+----+-------+-------+------+ 
| texto | value | n | -- | texto | value | n | 
+-------+-------+------+----+-------+-------+------+ 
| aaa | 10 | 1 | -- | aab | 11 | 1 | 
+-------+-------+------+----+-------+-------+------+ 

没关系。不过，我想是这样的：

+-------+-------+------+----+-------+-------+------+ 
| texto | value | n | -- | texto | value | n | 
+-------+-------+------+----+-------+-------+------+ 
| aaa | 10 | 1 | -- | aab | 11 | 1 | 
+-------+-------+------+----+-------+-------+------+ 
| aaa | 10 | 2 | -- | NULL | NULL | NULL | 
+-------+-------+------+----+-------+-------+------+ 

Answer 1

select a.*, '--', b.* 
    from mmm a 
left join mmm b on (a.n=b.n) 
where (a.value < b.value or b.value is null) 
    and a.texto ='aaa' 
    and (b.texto='aab' or b.textto is null); 

或：

select a.*, '--', b.* 
    from mmm a 
left join mmm b on (a.n=b.n and a.value < b.value and b.texto = 'aab') 
where a.texto ='aaa' ;