Data extraction. 3NF. php?

Question

PHP

Something I can't google... How to efficiently pull data from related tables? So far, this is the only way: knowing the entity_ID from the main table, we make a query with WHERE? for its table, and then, using PHP, we scatter the array into variables? Now we need to make a user's personal account with registration and viewing of already created orders, but I practically did not encounter databases.

Answer 1

Read about Joins

select from "основная таблица" от
  inner join "связанная таблица" ст on ст.relation_id = от.id
where <другие условия>