Dependency Preserving Decomposition

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Dependency Preserving Decomposition 

If we decompose a relation R into relations R1 and R2, All dependencies of R either must be a part of R1 or R2 or must be derivable from  FD’s of R1 and R2.  

Relation R is decomposed in to R1 and R2 with FDs F1 and F2 respectively  ,  if the decomposition is dependency preserving then

F1 U F2 =F


                                             and so           ( F1 U F2 ) + =F+



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