外连接查询条件顺序的对查询结果的影响

[_XuDaojie]

select 
c.name_check_state, 
a.no_bill, 
from 
ls_requisition_2 as b 
left join 
ls_requisition_1 as a on a.no_bill = b.no_body 
left join 
ls_item as c on c.no_ls = b.no_item; 

select 
c.name_check_state, 
a.no_bill, 
from 
ls_requisition_2 as b 
left join 
ls_requisition_1 as a on b.no_body  = a.no_bill 
left join 
ls_item as c on b.no_item = c.no_ls; 

我想知道我的a,no_bill = b.no_body 顺序反一下有什么区别啊 就是因为我顺序写反了所以结果没查询出来
是不是我把如果我把left join改成right join 是不是不用换顺序也可以呢

[發糞塗牆]

from a (left/right/full) join b on xxxx (left/right/full) join c on xxxx 它的执行顺序是先a与b关联，然后生成一个虚拟表假设叫做D，然后d与c再关联，本身你的顺序是没有太大影响，但是你在on中这样调换，需要了解你的表里面是否有符合条件的数据，这属于逻辑问题，不是写法问题。