How to pull data from Magento table?

Question

Magento

There are 3 tables 1-table of categories, 2-table of stocks (custom), 3-table linking the 1st and 2nd tables one-to-many. Two questions:
1) Is there a category id and how to pull out all the shares by this id, i.e. from the 2nd table?
2) Is there a category id and how can I extract all the data from the 3rd table using this id?
How to do all this in magento ways? ORM? Thank you)

Answer 1

You need to add a join to the category collection before calling load.
Documentation https://framework.zend.com/manual/1.10/en/zend.db....

$categories->getSelect()->join(....);
$categories->load();