7. Which SELECT statement implements a self join?
SELECT item.part_id, type.product_id
FROM part item JOIN product type
ON item.part_id =! type.product_id;
SELECT item.part_id, type.product_id
FROM part item JOIN product type
ON item.part_id = type.product_id;
SELECT item.part_id, type.product_id
FROM part item JOIN part type
ON item.part_id = type.product_id;
SELECT item.part_id, type.product_id
FROM part item JOIN product type
ON item.part_id = type.product_id (+);​