# Question: Consider the relations r1 A B C r2 C D

Consider 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 Θ r3, and give an efficient strategy for computing the join.

## Answer to relevant Questions

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. ...For each of the following pairs of expressions, give instances of relations that show the expressions are not equivalent. a. ΠA(R − S) and Π A (R) – ΠA (S) b. σB < 4(AGmax(B)(R)) and ...Describe how to incrementally maintain the results of the following operations, on both insertions and deletions.a. Union and set differenceb. Left outer joinExplain the distinction between the terms serial schedule and serializable schedule.Most implementations of database systems use strict two-phase locking. Suggest three reasons for the popularity of this protocol.Post your question