Chapter 4 Building Conceptual Data Models
This section shows the graphic representation of various relationship properties.
| One-to-many relationship | Description |
|---|---|
|
Each division may have zero or more employees
Each employee may belong to zero or one division |
|
Each division must have one or more employees
Each employee may belong to zero or one division |
|
Each division may have zero or more employees
Each employee must belong to one and only one division |
|
Each division must have one or more employees
Each employee must belong to one and only one division |
|
Each division may have zero or more employees
Each employee must belong to one and only one division Each employee is identified uniquely by division number and employee number |
|
Each division must have one or more employees
Each employee must belong to one and only one division Each employee is identified uniquely by division number and employee number |
| One-to-one relationship | Description |
|---|---|
|
Each team works on zero or one project
Each project is managed by zero or one team |
|
Each team works on one and one project only
Each project is managed by zero or one team |
|
Each team works on zero or one project
Each project is managed by one and one team only |
| Many-to-many relationship | Description |
|---|---|
|
Each division may have zero or more employees
Each employee may belong to zero or more divisions |
|
Each division must have one or more employees
Each employee may belong to zero or more divisions |
|
Each division may have zero or more employees
Each employee must belong to one or more divisions |
|
Each division must have one or more employees
Each employee must belong to one or more divisions |
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