query optimization, PL-SQL Programming

Assignment Help:
1.( /5 marks) Suppose that a B+-tree index with the search key (dept_name, building) is available on
relation department. What would be the best way to handle the following selection?
?(building = “Watson”) ? (budget < 55000) ? (dept_name = “Music”)(department)
a. 2 marks for clearly showing an equivalent relation algebra expression using the
appropriate, well identified rule supplied in the textbook (e.g., the derivation with rule #
applied).
b. 1.5 marks for clearly explaining how the B+ tree index would be used to evaluate the
conditions involving attributes that are specified as part of the index
c. 1.5 marks for clearly explaining how the remaining conditions that involve attributes that
are not specified as part of the index would be evaluated
2. ( /5 marks) Show how to derive the following relational algebra equivalences by a sequence of
transformations using the relational algebra equivalence rules in Section 13.2.1. Hint: make sure
you clearly define all rules you use; as well identify which rule is being applied and apply only one
rule for each line in your solution – show your work.
a. ??1??2??3 (E) = ??1 (??2 (??3 (E))) (2 marks)
b. ??1??2 (E1 ??3 E2) = ??1 (E1 ??3 (??2 (E2))), where ?2 involves only attributes from E2 (3
marks)
3. ( /5 marks) Consider the two expressions ?? (E1 E2) and ?? (E1 ? E2).
a. Show using a concrete example that the two expressions are not equivalent in general
(3 marks). Hint: first identify what the difference is between natural join and left outer join
(what is extra in the left outer join), and then make sure you give the concrete relation instances
for E1 and E2 that result in a different expression result.
b. Give a simple condition on the predicate ?, which if satisfied will ensure that the two
expressions are equivalent. Hint: Think about what extra tuples you would have in the left

1
Some of the problems are adapted from “Database System Concepts”, 6th Edition, 2011, Avis Silberschatz, Henry
F. Korth, S. Sudarshan.
outer join, how they joined tuple is constructed, and a condition that will exclude these extra
tuples.
4. ( /5 marks) Explain how to use a histogram to estimate the size of a selection of the form ?A=v(r).
Hint: Divide the distribution into n buckets {rj | j ? [1,n]} and consider the two cases: Part 1) the
selection value v is greater than or equal to the largest value of a given bucket ri (2 marks) and Part 2) the
selection value v is “part way” between the max and min values of bucket ri+1. (3 marks).
5. ( /5 marks) Give an example of a relational algebra expression defining a materialized view and
two situations (for the differentials) such that incremental view maintenance is better than
recomputation (recomputing the materialized view from scratch) in one situation (2.5 marks),
and recomputation is better in the other situation (2.5 marks). Hint: think about different values for
x between 0 and 100, where you insert x% tuples are deleted.

Related Discussions:- query optimization

Table represents an extension - sql, Table Represents an Extension - SQL ...

Table Represents an Extension - SQL It describes how each tuple in a relation represents a true instantiation of some predicate and each true instantiation is represented by s

Advantages of pl/sql, Advantages of PL/SQL The PL/SQL is a high-perform...

Advantages of PL/SQL The PL/SQL is a high-performance transaction processing, completely portable language that offers the following advantages as shown: 1) Support for SQL

Max and min operator in sql, MAX and MIN operator in SQL Example: ...

MAX and MIN operator in SQL Example: (SELECT MAX (Mark) FROM EXAM_MARK WHERE StudentId = 'S1') (SELECT MIN (Mark) FROM EXAM_MARK WHERE StudentId = 'S1') Example

Query, ALTER TABLE bb_basketitem ADD CONSTRAINT bitems_qty_ck CHECK (quan...

ALTER TABLE bb_basketitem ADD CONSTRAINT bitems_qty_ck CHECK (quantity BEGIN INSERT INTO bb_basketitem VALUES (88,8,10.8,21,16,2,3); END; Brewbean’s wants to add a check

Keyword and parameter description - forall statement, Keyword &Parameter De...

Keyword &Parameter Description: index_name: This is an undeclared identifier which can be referenced only within the FORALL statement and only as the collection subscript

program for employees -ado.net framework , Challenge 1 You are require...

Challenge 1 You are required to do the project and write a test plan for it. Demo 4 is a check writer program for employees. In it, the user enters all information about the

Updating a variable, Updating a Variable Assignment of an attribute va...

Updating a Variable Assignment of an attribute value in a variable of a structured type Synatx: SET SN.C = 'S2'; As in Example the entire statement is equivalent to a

Using prior and next - collection method, Using PRIOR and NEXT The PRI...

Using PRIOR and NEXT The PRIOR(n) returns the index number that precede index n in a collection. The NEXT(n) returns the index number which succeed the index n. If n has no pr

Short-circuit evaluation-pl/sql expressions , Short-Circuit Evaluation ...

Short-Circuit Evaluation When computing a logical expression, the PL/SQL uses short-circuit evaluation. That is, the PL/SQL stops computing the expression as soon as the result

Python function, This task involves developing some functions that extract ...

This task involves developing some functions that extract data from an SQL database. The scenario is that a company which owns an online vehicle search website wants to generate so

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd