User Account

All Pages

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

Creating and destroying base tables, Creating and Destroying Base Tables: ...

Creating and Destroying Base Tables: Example shows an SQL command to create the base table counterpart of the ENROLMENT variable Example  Creating a base table. CREATE T

Cursor attributes in pl sql, Cursor Attributes   The Cursors and curso...

Cursor Attributes   The Cursors and cursor variables have 4 attributes which give you helpful information about the execution of a data manipulation statement. Syntax:

Defining autonomous transactions, Defining Autonomous Transactions To ...

Defining Autonomous Transactions To define an autonomous transaction, you use the pragma (compiler directive) AUTONOMOUS_TRANSACTION. The pragma instructs the PL/SQL compiler

Explicit cursor attributes, Explicit Cursor Attributes The cursor varia...

Explicit Cursor Attributes The cursor variable or each cursor has four attributes: %FOUND, %ISOPEN, %ROWCOUNT, and %NOTFOUND. When appended to the cursor or cursor variable, th

Sqls counterpart of the key words, SQLs counterpart of the key words: ...

SQLs counterpart of the key words: The text from the opening parenthesis to the end of the fourth line specifies the declared type of the table, meaning that every table ever

Write sql code that will create the writes table, Question: Consider th...

Question: Consider the following relations (primary keys are underlined): AUTHOR (ANo, aname, address, speciality) PUBLISHER (PNo, pname, Location) BOOK (BNo, Title, ISBN,

Usefulness of data type, Usefulness of Data Type In SQL, as in most c...

Usefulness of Data Type In SQL, as in most computer languages, a type can be used for constraining the values that are permitted to be used for some purpose. In particular, i

Close statement in pl sql, CLOSE Statement The CLOSE statement allows ...

CLOSE Statement The CLOSE statement allows the resources held by a cursor variable or open cursor to be reused. No more rows can be fetched from the cursor variable or closed

Iteration schemes- iterative control, Iteration Schemes The bounds of a ...

Iteration Schemes The bounds of a loop range can be variables, literals, variables, or expressions but must compute to integers. Below are some of the examples. As you can see t

Definition of cross join - sql, Definition of CROSS JOIN - SQL Let s ...

Definition of CROSS JOIN - SQL Let s = t1 CROSS JOIN t2, where t1 and t2 are table expressions optionally accompanied by range variables. Then: Note: Here T denotes Table

Write Your Message!

Captcha
Order Assignment

Featured Services

Order Now

Popular Subjects

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!

Submit Assignment

Academics

Major Subjects

Majors

Get In Touch

whatsapp: +91-977-207-8620

Phone: +91-977-207-8620

Email: [email protected]

TERMS & POLICIES

HELP & SUPPORT

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