Microsoft 9GD00001 manual Foreign key relationship Save warning message

190Microsoft Visual Studio 2010: A Beginner’s Guide

Figure 7-8 Foreign key relationship Save warning message

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Figure 7-7 shows an editable Relationship Name field. In many cases, you won’t care what this name is because it follows a standard convention of FK_Child_Parent. However, sometimes you have multiple relationships between the same tables, which means that VS appends an incremental number to the end of the name. Thus, for instance, the next foreign key relationship between the same two tables would be FK_Child_Parent1. In those cases, it would be smart to plan ahead and change the name to something meaningful so that you can later understand or quickly recall what relationship rules the foreign keys are enforcing. To see what I mean by enforcing rules, go ahead and enter a new record in the Order table, but enter an integer in the CustomerID column that does not exist already in the Customer table, like 9999. Try to save that record and then read the error message presented to you.

Working with multiple tables, you might want to have a better feel for the database structure and relationships. Database diagrams could be helpful in this case. To create a database diagram, right-click the Database Diagrams folder under the database in Server Explorer and click Add New Diagram. Click Yes when you receive an information message requesting the creation of objects for database diagramming. In the Add Table window, press the CTRL key so that you can select multiple rows, click to select each table, and click Add. You’ll see a new database diagram similar to Figure 7-9 (you may see Order appear above Customer in your diagram, which is fine; the position of