Access 2002 Programming by Example

Referential Integrity

Notice in Figure 2.13 that the only records that match are 4 through 6. If you hook up the two tables with a left join, then you are going to have three dangling records in table B. If table A is Customers and table B is Orders, you have orders without Customers.

Figure 2.13. This diagram shows that table B has no matching records for records 1 through 3 in table A.

Referential integrity states that a value may not be added to a table with a foreign key without a corresponding value existing in the table being referenced. In layman’s terms, a matching value must exist in table A before it can be entered in table B. If ...