Establishing Referential Integrity
As you can see, establishing a relationship is quite easy. Establishing the right kind of relationship is a little more difficult. When you attempt to establish a relationship between two tables, SQL Server makes some decisions based on a few predefined factors:
A one-to-many relationship is established if one of the related fields is a primary key or has a unique index.
A one-to-one relationship is established if both the related fields are primary keys or have unique indexes.
A relationship cannot be created if neither of the related fields is a primary key and neither has a unique index.
As covered earlier in this chapter, referential integrity consists of a series of rules that SQL Server applies to ensure ...
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