Kuidas valida andmeid mitmest tabelist?

To select data from multiple tables in a relational database, the SQL JOIN operator is used. JOIN allows combining rows from two or more tables based on a related column.

For example, if there is an orders table and a customers table, to get a list of orders with customer names, you can write:

SELECT orders.id, customers.name, orders.amount
FROM orders
JOIN customers ON orders.customer_id = customers.id;

Depending on the task, different types of JOIN can be used: INNER JOIN (only matching records), LEFT JOIN (all from the left table and matching from the right), RIGHT JOIN, etc.