The ISRO Computer Science (CS) Scientist Engineer test held on April 22, 2007 (Sunday). Total questions were 80 and test duration were 90 Minutes. Here is the solution of paper according to me of set A.
- The Answer Key 2007 for Set A Non-Official by Me: Click here (By ISRO not available)
- For complete preparation for ISRO Computer Science visit my this article: Click Here
- For ISRO Answer Key and Solutions Computer Science Scientist Engineer 2016: Click here
- For ISRO Answer Key and Solutions Computer Science Scientist Engineer 2015: Click here
- For ISRO Answer Key and Solutions Computer Science Scientist Engineer 2014: Click here
- For ISRO Answer Key and Solutions Computer Science Scientist Engineer 2013: Click here
- For ISRO Answer Key and Solutions Computer Science Scientist Engineer 2011: Click here
- For ISRO Answer Key and Solutions Computer Science Scientist Engineer 2009: Click here
- For ISRO Answer Key and Solutions Computer Science Scientist Engineer 2008: Click here
47. Which commands are used to control access over objects in relational databases?
(a) CASCADE & MVD
(b) GRANT & REVOKE
(c) QUE & QUIST
(d) None of these
Correct Answer: (b)
Explanation: The Data Control Language (DCL) is a subset of the SQL that allows database administrators to configure security access to relational databases. It consists of only three commands: GRANT, REVOKE, and DENY.
Reference: http://databases.about.com/od/Advanced-SQL-Topics/a/Data-Control-Language-Dcl.htm48. Which of the following is aggregate function in SQL?
(a) Avg
(b) Select
(c) Ordered by
(d) distinct
Correct Answer: (a)
Explanation: SQL aggregate functions return a single value, calculated from values in a column. Useful aggregate functions: AVG() - Returns the average value. COUNT() - Returns the number of rows.
Reference: SQL Functions - W3Schools50. A view of a database that appears to an application program is known as
(a) Schema
(b) Subschema
(c) Virtual table
(d) None of these
Correct Answer: (b)
Explanation: The external level is the user’s view of the database and closest to the users.This level describes that part of the database that is relevant to the user.
Reference: http://gateoverflow.in/51119/view-of-database-that-appears-to-an-application-programmer- Most of the users of database are not concerned with all the information contained in the database. Instead, they need only a part of the database relevant to them.
- An subschema describes each external view. The subschema consists of the definition of the logical records and the relationships in the external view.
The sub-schemas appears to application program to perform the operations.
51. Armstrong's inference rule doesn't determine
(a) Reflexivity
(b) Augmentation
(c) Transivity
(d) Mutual dependency
Correct Answer: (d)
Explanation: We can derive additional functional dependencies from the initial set using inference rules. Armstrongs's Axioms are most basic inference rules. These are 3 rules:
- Reflexivity: If Y is a subset of X, then X → Y
- Augmentation: If X → Y, then XZ → YZ
- Transitivity: If X → Y and Y → Z, then X → Z
Additionally there are secondary rules derived from above 3 rules:
- Union: If X → Y and X → Z, then X → YZ
- Decomposition: If X → YZ, then X → Y and X → Z
- Pseudotransitivity: If X → Y and WY → Z, then WX → Z
- Composition: If X → Y and Z → W, then XZ → YW
52. Which operation is used to extract specified columns from a table?
(a) Project
(b) Join
(c) Extract
(d) Substitute
Correct Answer: (a)
Explanation: Project operation (∏) is used to select (extract) columns from a table that satisfy a given conditions.
Reference: http://www.tutorialspoint.com/dbms/relational_algebra.htm54. BCNF is not used for cases where a relation has
(a) Two (or more) candidate keys
(b) Two candidate keys and composite
(c) The candidate key overlap
(d) Two mutually exclusive foreign keys
Correct Answer: __
Explanation: To figure out correct option, following points require our attention:
Reference: https://www.gatementor.com/viewtopic.php?f=268&t=8444- When a key is composed of more than one column, it is known as a composite key.
- A candidate key is a column (Simple Candidate Key), or set of columns (Composite Candidate Key), in a table that can uniquely identify any database record without referring to any other data. Each table may have one or more candidate keys.
- BCNF asks "are all attributes to the left of the arrows candidate keys?", if yes then its BCNF.
- Mutually Exclusive means can't happen at the same time.
And now check options one by one:
- Option (a) is a case for BCNF by seeing point 3 above.
- Option (c) is a case for BCNF because there is candidate keys are overlapping (e.g. AB, AC, AD) and it is okay for BCNF.
60. Which of the following is correct with respect to Two phase commit protocol?
(a) Ensures serializability
(b) Prevents Deadlock
(c) Detects Deadlock
(d) Recover from Deadlock
Correct Answer: None of These
Explanation: Two-phase commit (2PC) protocol should not be confused with the two-phase locking (2PL) protocol, a concurrency control protocol. 2PL is a concurrency control method that guarantees serializability. 2PC is a distributed algorithm that coordinates all the processes that participate in a distributed atomic transaction.
Reference: https://en.wikipedia.org/wiki/Two-phase_commit_protocol69. A rule in a limited entry decision table is a
(a) row of the table consisting of condition entries
(b) row of the table consisting of action entries
(c) column of the table consisting of condition entries and the corresponding action entries
(d) columns of the table consisting of conditions of the stub
Correct Answer: (c)
Explanation: The limited-entry decision table is the simplest to describe. The condition alternatives are simple Boolean values, and the action entries are check-marks, representing which of the actions in a given column are to be performed.
Reference: https://en.wikipedia.org/wiki/Decision_table
thanx
ReplyDeleteGreat. .keep posting
ReplyDelete