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Cascades

What are cascades? You can think of it this way: If you change a value in one table, it is automatically cascaded or updated in another table, regardless of how many records are tied to that record in the other table. Similarly, if you delete a value in one table, the corresponding records in the other table are also deleted. The former works at the field level, and the latter works at the record level. So, when you change primary key values or delete records in a primary table, Access automatically makes necessary changes to related tables so that referential integrity is preserved.

If you change a customer’s number, you want his orders to be updated to reflect this change. Otherwise, his orders are not synchronized. In the same manner, if you delete this customer, you also want his orders deleted. This is another distinction from the query design.


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