Using Join Types
When a view includes data from more than one table, you can choose from two types of joins when creating a view:
An inner join returns the records selected for the first table combined with related records selected from the second table. If a record does not exist in the second table, no records are returned. Only related records selected from both sides of the relationship display in the view.
An outer join returns the records found by an inner join. However, in addition, for each value in the first table, it returns unknown values from the second table when no related record is found. As a result, all matching records from the first table are preserved for unmatched records in the second table.
The default join type is inner. Using the outer join can give you more flexibility in displaying information.
Example: An inner join between customers and sales orders displays only customers with sales orders. An outer join includes all customers, even those who do not have orders.