Explain the use of constraints in functional model, Database Management System

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Explain the use of constraints in functional model with suitable example.

A constraint shows relationship between two objects at same time, or   among various values of the same object at different times. A constraint can be expressed as a total function or as the partial function. For instance, a coordinate transformation may specify that scale factor for x-coordinate and the y-coordinate will be equal. This constraint completely defines one value in terms of the other values

 


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