Clustering indices may allow faster access to data than a nonclustering index affords. When must we create a nonclustering index, despite the advantages of a clustering index? Explain your answer.
Answer to relevant QuestionsConsider the relations r1 (A, B, C), r2 (C, D, E), and r3 (E, F), with primary keys A, C, and E, respectively. Assume that r1 has 1000 tuples, r2 has 1500 tuples, and r3 has 750 tuples. Estimate the size of r1 Θ r2 ...Show how to derive the following equivalences by a sequence of transformations using the equivalence rules in Section 14.3.1. a. σθ1 ∧ θ2 ∧ θ3 (E) = σθ1 (σθ2 ...Decorrelation:a. Write a nested query on the relation account to find for each branch with name starting with “B”, all accounts with the maximum balance at the branch.b. Rewrite the preceding query, without using a ...Justify the following statement: Concurrent execution of transactions is more important when data must be fetched from (slow) disk or when transactions are long, and is less important when data is in memory and transactions ...What benefit does rigorous two-phase locking provide? How does it compare with other forms of two-phase locking?
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