Descriptive

(a) The following table refers to search times for a key in B-trees and B⁺-trees.

A successful search means that the key exists in the database and unsuccessful means that it is not present in the database. Each of the entries X₁, X₂, X₃ and X₄ can have a value of either Constant or Variable. Constant means that the search time is the same, independent of the specific key value, where Variable means that it is dependent on the specific key value chosen for the search.

Give the correct values for the entries X₁, X₂, X₃ and X₄ (for example X₁ = Constant, X₂ = Constant, X₃ = Constant, X₄ = Constant).

(b) Relation R(A,B) has the following view defined on it:

 CREATE VIEW V AS
 (SELECT R1.A, R2.B
 FROM R AS R1, R AS R2
 WHERE R1.B = R2.A)

(i) The current contents of relation R are shown below. What are the contents of the view V?

(ii) The tuples (2,11) and (11,6) are now inserted into R. What are the additional tuples that are inserted in V?