MySQL查询子查询? [英] MySQL query subquery?

问题描述

好的，这是我正在使用的数据:

OK this is the data I am working with:

category_child_id category_parent_id
                1                  0
                2                  0
                3                  1
                4                  1
                5                  3
                6                  3
                7                  4
                8                  0
                9                  8
               10                  8
               11                  0
               12                 11
               13                 11
               14                  0
               15                 14
               16                 14
               17                 14
               18                  0
               19                 18
               20                 18
               21                 18
                0                 19

它基本上是带有子类别等的类别.

如果我

从category_xref中选择category_child_id，category_parent_id = 1
它返回3& 4，这是正确的.但是，仅在下面的类别中没有该类别的产品，因此我实际想要的结果是5&. 6.但是，这并不总是相同的，因此确实需要进行查询.

因此，基本上我需要运行查询以从表中获取所有已连接(嵌套)的类别.我已经尝试了多种方法，但均以失败告终，因此任何帮助都将非常有用.

It''s basically categories with sub categories etc etc.

If I

SELECT category_child_id FROM category_xref WHERE category_parent_id = 1
it returns 3 & 4 which is correct. However there are no products in this category only in the category below so the results I actually want are 5 & 6 as well. However this is not always the same so it does need to be a query.

So basically I need to run a query to get all connected(nested) categories from the table. I''ve tried many ways with failed results so any help would be great.

推荐答案

尝试一下此方法

Try this

select B.category_child_id from category_xref A inner join category_xref B
on A.category_child_id = B.category_parent_id
where (A.category_parent_id = 1 or B.category_parent_id = 1)

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