MySQL query subquery?

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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

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.

Posted 2-Apr-12 2:18am

Paul Hayman

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sachin10d · Answer 1 · 2012-04-02T03:24:00

Solution 1

Try this

SQL

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)

Posted 2-Apr-12 3:24am

sachin10d