I have 2 tables. The first table is feeds and (feeds.ID) is the primary key. The second table is items. feeds.ID is related to items.feed_ID, so with a simple inner join I can extract the data of each feed.
Now, I deleted some of the feeds but didn't delete them from the items table. I want to find the items which have no resource on the feeds table. On the other hand, I want to find the useless items. What is the correct query?
I have tried this:
select * from items where feed_id NOT IN (select id from feeds inner join items on feeds.id=items.feed_id group by feed_id) group by feed_id
but it shows an error.