# Question

Consider the relations r1 (A, B, C), r2 (C, D, E), and r3 (E, F) of Exercise. Assume that there are no primary keys, except the entire schema. Let V (C, r1) be 900, V (C, r2) be 1100, V (E, r2) be 50, and V (E, r3) be 100. Assume that r1 has 1000 tuples, r2 has 1500 tuples, and r3 has 750 tuples. Estimate the size of r1 Θ r2 Θ r3, and give an efficient strategy for computing the join.

## Answer to relevant Questions

Suppose that a B+-tree index on branch-city is available on relation branch, and that no other index is available. What would be the best way to handle the following selections that involve negation? a. σ ¬ ...SQL allows relations with duplicates. a. Define versions of the basic relational-algebra operations σ, Π, ×, Π, −, ∪, and ∩ that work on relationswith duplicates, in a way consistent with ...Give an example of an expression defining a materialized view and two situations (sets of statistics for the input relations and the differentials) such that incremental view maintenance is better than recomputation in one ...Consider the following two transactions: T1: read (A); read (B); if A = 0then B: = B + 1; write (B). T2: read (B); read (A); if B = 0 then A: = A + 1; write (A). Let the consistency requirement be A = 0 ∨ B = 0, ...Consider a database organized in the form of a rooted tree. Suppose that we insert a dummy vertex between each pair of vertices. Show that, if we follow the tree protocol on the new tree, we get better concurrency than if we ...Post your question

0