Progress
Database Design
Guide


One-to-one Relationship

A one-to-one relationship exists when each row in one table has only one related row in a second table. For example, a business may decide to assign one office to exactly one employee. Thus, one employee can have only one office. The same business may also decide that a department can have only one manager. Thus, one manager can manage only one department. Figure 2–3 shows this relationship.

Figure 2–3: Examples of a One-to-one Relationship

However, the business may also decide that for one office there is zero or one employee; for one department there is no manager or there is one manager then the relationship is described as a zero-or-one relationship.


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