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If P and Q are predicates and P is the relational algebra expression, then which of the following equivalences are valid ?

If P and Q are predicates and P is the relational algebra expression, then which of the following equivalences are valid ?

A σ_P(σ_Q(e))=σ_Q(σ_P(e))

B σ_P(σ_Q(e))=σ_Q(e)

C nσ_Q(σ_P(e))=σ_Q(σ_P(e))

D none of these

Answer & Explanation
Option: [D]

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