Introducing Data Relationships
Herein lies the beauty of relational databases. Instead of keying in customer information for each of my orders and then duplicating the effort when I add new customers to the Customers table, I can link the data across tables.
Linking or relating data is the act of sharing it between two or more tables. When you input new data or update existing data, it is automatically updated across all tables.
Figure 4.4 illustrates the relationships on the map.
Figure 4.4. The lines on the map show where data will be linked between tables.
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