The Constraints tab contains the following tools:
Tool
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Description
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![](../image/pendeb1322884107771_3-rad1232636988301.image)
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Add Key Constraint - The element value must be a key within the specified scope. The scope of a key is the containing element in an instance document. A key must be unique, not null, and always present
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![](../image/pendeb1322884107771_3-rad1232636990051.image)
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Add Unique Constraint - The element value must be unique or null within the specified scope
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![](../image/pendeb1322884107771_3-rad1232636992223.image)
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Add KeyRef Constraint - The element value corresponds to those of the specified key or unique constraint
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For general information about creating objects, see Core Features Guide > The PowerDesigner Interface > Objects.