Microsoft Office Tutorials and References
In Depth Information
One-to-Many Relationships
Figure 2-38
One-to-many relationship and sample query
primary table
two c ontracts for
customer 11045
common field
related table
fields from the
Customer table
fields from the
Contract table
query that joins fields
from the Customer
and Contract tables
One-to-Many Relationships
As shown earlier in the Session 2.2 Visual Overview, a one-to-many relationship exists
between two tables when one record in the fi rst table matches zero, one, or many
records in the second table, and when one record in the second table matches at most
one record in the fi rst table. For example, as shown in Figure 2-38, customer 11045 has
two contracts in the Contract table. Other customers have one or more contracts. Every
contract has a single matching customer.
Access refers to the two tables that form a relationship as the primary table and the
related table. The primary table is the “one” table in a one-to-many relationship; in
Figure 2-38, the Customer table is the primary table because there is only one customer
for each contract. The related table is the “many” table; in Figure 2-38, the Contract table
is the related table because a customer can have zero, one, or many contracts.
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