mySQL Query over multiple tables

Question

Help needed please! I need to grab the entry_id’s relating to cat_id of ’42’, then find all cat_id’s that are attached to the entry_id’s we have just filtered by. I then need to get the cat_group_id of them cat_id’s. See screenshots of tables below:

EDIT

E.g. entry_id 92 has cat_id 42 assigned to it. But it also has 48 & 71. It's these numbers I need to output. But only if the entry_id is in cat_id 42

What all have you tried so far? Show the code you've tried that does not work for better results here. — Jason
– Jason, Commented Nov 10, 2015 at 11:42
Sadly, I'm not 100% on MySQL. The furthest I got was a simple Select, as well as trying to grab data from multiple tables. Nothing in the direction I needed really. — Jason Mayo
– Jason Mayo, Commented Nov 10, 2015 at 13:44

pedromendessk · Accepted Answer · 2015-11-10 15:10:57Z

1

I didn't understand very well what you wanted, is it this?

select
  group_id
from
  exp_categories
inner join
  exp_category_posts
  on exp_category_posts.cat_id = exp_categories.cat_id
where
  entry_id in (select entry_id from exp_category_posts where cat_id = 42)
;

Note: I didn't create the tables to test it, but I think the query is ok

edited Nov 10, 2015 at 15:10

answered Nov 10, 2015 at 12:27

pedromendessk

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2 Comments

Jason Mayo Over a year ago

Because I need to filter the entries down to see if they exist in cat_id 42 first. Then if they do, find all the other cat_id's assigned to the entry_id's that return true to cat_id = 42. If theres an easier way of doing this...

Jason Mayo Over a year ago

Amazing. That works. I didn't need the group_id but the cat_id in the end, so I just changed 'select group_id' to 'select exp_categories.cat_id' and that worked a charm! THANKYOU

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