MCQ on various aspects in DBMS including database indexing, join techniques, hashing ideas, and disk properties with answers, RDBMS Multiple Choice Questions with Answers
Database Management Systems (DBMS) MCQ Quiz Questions with Answers
1. Adding indexes
to a table would help in speeding-up the execution. Clustered indexes can
perform better than non-clustered indexes. But, you can create more
non-clustered indexes than the clustered index .
Why?
a) Because
clustered indexes take more space than non-clustered indexes and the database
servers has little space.
b) Because a
relation can have only one clustered index, but many non-clustered indexes.
c) Because
clustered indexes will slow down updates and the application has many updates.
d) None of the
above
View Answer
Answer:
(b) Because a relation can have only one clustered index, but many
non-clustered indexes
A
clustered index defines the order in which data is physically stored in a
table. Hence, only one clustered index is possible.
Non-clustered
indexes are created on other attributes and the values in that attributes
need not be stored in some order in the source table.
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2. To execute a
query in a database, we have both logical and physical operators. Which of the
following is physical operator?
a) Equi-join
b) Natural join
c) Merge join
d) Theta join
View Answer
Answer:
(c) Merge join
Logical
operators describe the relational algebraic operation used to process a
statement. In other words, logical operators describe conceptually what
operation needs to be performed.
Physical
operators implement the operation described by logical operators.
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3. How many blocks
are on a disk with the following characteristics? Sector size of 512 bytes, 8
sectors per track, 8192(16384) tracks per surface, 4 double sided platter, and
4096 bytes per block.
a) 262144 blocks
b) 65536 blocks
c) 131072 blocks
d) None of the
above
View Answer
Answer:
(b) 65536 blocks
Number
of blocks for the disk with the given properties can be calculated as
follows;
512
bytes * 8 sectors * 8192 tracks * 4 platters * 2 sides / 4096 bytes = 65536
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4. How do we refer
the query that is written under the WHERE clause or HAVING clause of another
SQL query?
a) Query
b) Nested query
c) Sub-query
d) Secondary query
View Answer
Answer:
(b) Nested query and (c) Sub-query
A
sub-query or nested query is a SELECT statement that is written within another
SQL query.
Example:
SELECT
* FROM student WHERE regno IN (SELECT regno FROM marks WHERE avg = 100);
The
query given inside the parenthesis is called sub-query
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5. The hashing
technique that allows a hash file either to expand or to shrink dynamically is
__________.
a) Extendible
hashing
b) Linear hashing
c) Non-linear
hashing
d) External hashing
View Answer
Answer:
(a) Extendible hashing
Extendible
hashing is a dynamically updateable disk-based index structure which
implements a hashing scheme utilizing a directory.
The
dynamic aspects of extendible hashing are handled by two mechanisms;
Insertion
and bucket splitting – to handle bucket overflow, the bucket is split into
two.
Deletion
and bucket combining – to handle empty buckets, they can be combined with
other buckets.
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Related posts:
- Go to Multiple Choice Questions in DBMS home
- Go to Normalization - MCQs page
- Go to General Mixed Quiz in all topics of DBMS page
Go to Advanced DBMS Concepts page
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