SQL——联结

一、联结的种类

二、自联结（一张表）

select *
from table AS *, table AS **
WHERE *._ = **._
AND _ _ _ 

-- 已知出问题的产品ID,在产品表中寻找此产品的供应商，并列出该供应商其他所有产品信息（同一张表）
select *
from products as A , products as B
where A.vend_id = B.vend_id 
and B.prod_id = "DTNTR";

 自联结也可以用子查询结合WHERE来实现

select * from products
WHERE vend_id in (select vend_id 
		from data.products
		where prod_id = "DTNTR");

三、内部联结/等值联结（inner join  =  join）

select **
from * inner join *
on * = *