Explain the principle of LEFT JOIN in SQL and how it differs from other types of joins.

LEFT JOIN in SQL is used to combine two tables in such a way that all records from the left (first) table and the matching records from the right (second) table are included in the result. If there are no matches for a row in the left table, NULL values will be used for the columns of the right table.

Differences from other types of JOIN:

• INNER JOIN returns only the records that match in both tables.
• RIGHT JOIN returns all records from the right table and the matching ones from the left.
• FULL OUTER JOIN returns all records from both tables, filling in NULLs where there are no matches.

Example of LEFT JOIN:

SELECT A.id, A.name, B.order_date
FROM Customers A
LEFT JOIN Orders B ON A.id = B.customer_id;

This will display all customers, even if they have no orders (in this case, order_date will be NULL). This is useful when you want to keep all data from the main table and supplement it with information from the related table if available.