如何在一张表上两次用左连接同一张表

表一是表二的子集，有必要用左连接吗？直接等连就行了，用个union全解决了
select teacher_id as id,people_name as name
from 表1,表2
where
表1.teacher_id=表2.people_id
union select student_id as id,people_name as name
from 表1,表2
where
表1.student_id=表2.people_id

select b1.people_name teacher_name, b2.people_name student_name
from 表1
left join 表2 b1 on teacher_id = b1.people_id
left join 表2 b2 on student_id = b2.people_id

select b.people_name,c.people_name
from 表1 a，表2 b，表2 c
where a.teacher_id=b.people_id and a.student_id=c.people_id

例如： select *
from CT_CYK_CustomerBaseInfo
LEFT OUTER JOIN T_BD_Customer ON CT_CYK_CustomerBaseInfo.CFCustNameID=T_BD_Customer.FID
and CT_CYK_CustomerBaseInfo.CFMainLinkMenID=T_BD_Customer.FID;

把客户的基本信息表进行的重新命名，然后修改了sql语句，取得成功，结果如下：
select *
from CT_CYK_CustomerBaseInfo
LEFT OUTER JOIN T_BD_Customer ON CT_CYK_CustomerBaseInfo.CFCustNameID=T_BD_Customer.FID
LEFT OUTER JOIN T_BD_Customer as linkpeople ON
CT_CYK_CustomerBaseInfo.CFMainLinkMenID=linkpeople.FID;
这样就实现了在一个数据库表中同时两次左联接。