Left Outer Joins

Left Outer Joins connect all of the rows of data in the table with the primary key
with any row in the related table that has a matching foreign key.

All rows in the “primary” (“left”) table are displayed,
regardless of whether there is a matching record in the related table.

Remember that a relationship, even with “Referential Integrity” enforced,
may have a record in the primary table that has no matching record in the other table.

This is not really a problem, as in the case of the “Customer / Orders” example.

It is quite possible for a customer to have no orders,
but a “Left Outer Join” could find customers who haven’t bought anything,
so the store owner might send them a catalog ?

Or, maybe just know which names to delete from their mailing list to save postage ?

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