SQL: Struggling with DELETES

Question

I need to delete records in a table that are based on joins
of other tables.
Getting the data via joins is easy, but I'm struggling to
figure out how to
delete items from one table based on a join from multiple
tables.
Heres one example:
I have two tables, items and categories.
To get the rows from items, I can use a join:
SELECT *
FROM items INNER JOIN
categories ON items.categoryID =
categories.categoryID
WHERE (items.categoryID = 9) OR
(categories.categoryParentID = 9)
Now, what if I want to delete the records from items, but not
delete any
records from categories?
Can I just use?:
DELETE FROM items INNER JOIN
categories ON items.categoryID =
categories.categoryID
WHERE (items.categoryID = 9) OR
(categories.categoryParentID = 9)
-Darrel

Answer 1

Lionstone:
Have time to help me with another one? ;o)
So, the next challenge is pretty much the same thing, but
with a
double-join. The query I use to get the data is such:
SELECT * FROM WeFAQsVariations INNER JOIN
WeFAQs faqs ON vars.collectionID = faqs.collectionID
INNER JOIN
We_about_categories cats ON faqs.categoryID =
cats.categoryID
WHERE (faqs.categoryID = 9) OR (cats.categoryParentID = 9)
I want to delete the records from WeFAQsVariations where the
collectionID
matches the colletionID of the record in the FAQs table where
the categoryID
is or is a child of '9'
I didn't get very far on this one, though, as the simple
delete command:
DELETE FROM WeFAQsVariations
WHERE collectionID = ?
won't work, as I'm going to be returning a bunch of different
collectionIDs.
I think I need the EXISTS condition:
DELETE FROM WeFAQsVariations
WHERE EXISTS (
SELECT * FROM WeFAQs faqs INNER JOIN
We_about_categories cats ON faqs.categoryID =
cats.categoryID
WHERE (vars.collectionID = faqs.collectionID) AND
(faqs.categoryID = 9 OR
cats.categoryParentID = 9)
Did I come close?
_Darrel