Which type of join returns all records from both entities, with NULLs for non-matching records?

The correct answer is the type of join known as an OUTER JOIN. An OUTER JOIN is designed to return all records from both entities involved in the join operation. For any records where there is no direct match between the two entities, the fields corresponding to the non-matching records will be filled with NULL values.

This is especially useful when you want to ensure that you retrieve all the information from both entities, regardless of whether they have a corresponding match in the other entity. For example, if one entity contains records of all customers and another contains records of orders, an OUTER JOIN would ensure you get all customers listed, with NULLs in the order fields for customers who haven't placed any orders, and all orders listed, with NULLs for customers who do not exist in the customer table corresponding to those orders.

The other types of joins have different functionalities. INNER JOIN only returns records with matches in both tables, while LEFT JOIN and RIGHT JOIN return all records from one table and matched records from the other, with NULLs for non-matches only on one side, not both.