How to merge three MySQL tables and exclude certain rows?

Question

MySQL

There are three tables:
1. A table with sciences
2. A table with learned sciences
3. A table indicating which science will open after learning a certain one.

There can be over 500 sciences, so I don’t want to display all the sciences at once, and there’s no point. It is necessary to display only those that can be studied, as well as hide those studied.

In my case, studied Agriculture and Livestock. They opened access for study: Milk, meat, wheel, iron.
Car and Rocket are not available. They need to be hidden.

I've been trying to do it for two days with the help of JOINs. It turns out nonsense. Can you please tell me how this can be implemented?

Answer 1

What can you do here for two days?

SELECT `s`.*
  FROM `learned_sciences` AS `l`
  JOIN `science_branch` AS `b` ON `b`.`science_id` = `l`.`science_id`
  JOIN `sciences` AS `s` ON `s`.`id` = `b`.`open_science_id`
  WHERE `l``user_id` = :iserId
    AND `s`.`id` NOT IN (
      SELECT `science_id`
        FROM `learned_sciences`
        WHERE `user_id` = :userId
    )