请采用以下sql脚本
select a.partno,c.unitna as [采购单位名称],d.unitna as [主单位名称]
from [tb1] as a left join [tb2] as b on a.partno = b.partno
left join [tb3] as c on a.setun = c.unitno
left join [tb3] as d on b.munit= c.unitno
请采纳!
比如有三张表,student,teacher , project :
第一种方法:select * from student,teacher,project where student.id=teacher.sid and student.id=project.sid;
第二种:select * from student inner join teacher on student.id=teacher.sid inner join project on student.id=project.sid;