A **full outer join** returns all rows from both tables, including any unmatched rows, whereas an **inner join** only returns rows that match the join condition between the two tables. For an example of each one, say you had sales data exported from Salesforce's Salesforce CRM stored in a datawarehouse which had two tables: sales and salesforce_customers. **INNER JOIN**: retrieves rows from both tables where there is a match in the shared key or keys. SELECT * FROM sales INNER JOIN salesforce_customers ON sales.customer_id = salesforce_customers.id This query will return rows from the sales and salesforce_customers tables that have matching customer id values. Only rows with matching customer_id values will be included in the results. **FULL OUTER JOIN**: retrieves all rows from both tables, regardless of whether there is a match in the shared key or keys. If there is no match, NULL values will be returned for the columns of the non-matching table. Here is an example of a SQL full outer join using the sales and salesforce_customers tables: SELECT * FROM sales FULL OUTER JOIN salesforce_customers ON sales.customer_id = salesforce_customers.id ---