NATURAL and FULL JOIN
FULL OUTER JOIN
A FULL OUTER JOIN, also referred to as a FULL JOIN, combines the characteristics of both LEFT JOIN and RIGHT JOIN, including all rows from both tables in the result set.
If there's a matching row between the tables based on the ON clause, the columns from both tables are populated. However, if a row in one table doesn't have a match in the other table, the columns from the unmatched table display null values.
SELECT customers.customer_name, orders.order_id
FROM sales.customers AS customers
FULL OUTER JOIN sales.orders AS orders ON customers.customer_id = orders.customer_id;
This query combines all rows from both the sales.customers and sales.orders tables, ensuring no data is excluded from either side. The ON clause establishes the relationship between the two tables by matching the customer_id column.
If a row in one table has no corresponding match in the other table, the unmatched columns return null values.
You would use this approach for a comprehensive view of all customers and orders, including scenarios where one doesn't have an associated record in the other.
NATURAL JOIN
NATURAL JOIN is a type of SQL join that simplifies the process of combining tables by automatically matching columns with the same name and compatible data types from both tables.
Unlike explicit joins, where the relationship between tables is defined using an ON clause, NATURAL JOIN relies on column names to identify shared attributes. It ensures that only rows with identical values in the matched columns are included in the result set, effectively filtering out mismatches.
This approach is useful when the tables being joined posses clearly defined relationships and matching column names, as it reduces the need for manual specification of join conditions.
However, users must exercise caution, as relying purely on column names can lead to unintended results if the tables contain columns with identical names but unrelated data.
SELECT c.customer_name, o.order_id
FROM sales.customers AS c
NATURAL JOIN sales.orders AS o;
This query combines the sales.customers and sales.orders tables by automatically matching columns with the same name and compatible data types, such as customer_id.