• Create BookmarkCreate Bookmark
  • Create Note or TagCreate Note or Tag
  • PrintPrint
Share this Page URL
Help

Chapter 8. Managing Relationships

Chapter 8. Managing Relationships

Relationships, or links between your tables, help Access manage your databases more efficiently. Relationships are the backbone of the entity-relationship model, which is in turn the essence of a relational database.

An entity is represented by a table, with each record in it representing an instance of the entity described by that table. A Customers table—the entity—with fields for name, address, and company name, describes "customers" in general, while each record—the instance—describes a specific customer.

Relational databases allow you to create a scheme that recognizes the interaction of entities. In the simplest case, you can establish relationships to link tables logically. For instance, in a relational database with tables that list customers and customer orders, you can define a connection between those tables based on a common field (in this case, probably a customer's identification number).

Relationships mean you don't have to store the same data repeatedly. If you have a table of customers and a table of orders related by a CustomerID field, you can find (and combine) records in both tables using a query. In unrelated tables, you either need to combine the records by hand or store the contact information with the record for each order.


PREVIEW

                                                                          

Not a subscriber?

Start A Free Trial


  
  • Creative Edge
  • Create BookmarkCreate Bookmark
  • Create Note or TagCreate Note or Tag
  • PrintPrint