| Home | A relational database has
relationships with multiple tables. In Microsoft Access, all tables have one primary key.
When a primary key in one table is linked to a record in another table,
that is called a foreign key. Relational databases also include queries
to find specific answers to questions in the data or to filter out data
not needed for the query and only display data relevant to the question. The sample database below includes a customer table, an inventory table, and an orders table. Obviously, the customer table includes customer's contact information and the inventory table includes information about the products in stock. The orders table includes three fields, which are an order number (primary key), a customer number (foreign key linked to the customer table), and an inventory number (foreign key linked to the inventory table). The customer number and inventory number in the orders table use "lookup fields" to link the data from those tables to the orders tables. I've included sample data in the database below to show the use of "lookup fields" in a relational database. Click here for a sample relational database (Microsoft Access file - 496 KB). |
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Click "Open" if prompted with this warning.
After the database is opened, you'll see the list of tables.
Click on the "Orders" table and you'll see plus signs next to each record. Click the plus sign to see the customer that placed that order. It's gathering that information from the customer's table. This shows the advantage of lookup fields.
Click on "Queries" and you'll see two simple queries.
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