What is the condition for a decomposition to be considered lossy?
Question
What is the condition for a decomposition to be considered lossy?
Solution
A decomposition is considered lossy if there is a loss of information during the process, which means that we cannot get the original relation from the decomposed relations. This usually happens when the decomposition is not dependency preserving. In other words, if the decomposition of a relation R into R1 and R2 does not satisfy the condition that (R1 ∩ R2) -> (R1 U R2) is a functional dependency in R, then the decomposition is lossy.
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