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本帖最后由 licong0527 于 2012-09-11 13:40 编辑
回复 4# cenalulu
按照楼主说的,我试了一下
(1)
select p1.prod_id as prod_id1, p1.prod_name as prod_name1, p1.vend_id as vend_id1 from products as p1, products as p2 where p1.vend_id = p2.vend_id and p1.prod_id = 'dtntr';
结果如下:
(2)
select p2.vend_id as vend_id2, p2.prod_id as prod_id2, p2.prod_name as prod_name2 from products as p1, products as p2 where p1.vend_id = p2.vend_id and p1.prod_id = 'dtntr';
结果如下:
(3)
select p2.vend_id as vend_id2, p2.prod_id as prod_id2, p2.prod_name as prod_name2 from products as p1, products as p2 where p1.vend_id = p2.vend_id and p2.prod_id = 'dtntr';
结果如下:
(4)
select p1.prod_id as prod_id1, p1.prod_name as prod_name1, p1.vend_id as vend_id1 from products as p1, products as p2 where p1.vend_id = p2.vend_id and p2.prod_id = 'dtntr';
结果如下:
规律我是发现了:select的表名和过滤条件中的表名要不一致时,才可以得到我们想要的效果。
不过,本人还是不理解为什么呢?
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