Introduction to Databases

Physical data independence is

• making changes at the conceptual level without affecting the physical level.

• making changes at the physical level without affecting the conceptual level.

• making changes at the external level without affecting the conceptual level.

• making changes at the conceptual level without affecting the external level.

• making changes at the physical level without affecting the external level.

In a banking system the following scenarios may take place.

(I) Account balance could go below the minimum allowed.

(II) Customers are able to find out the bank balance of other customers.

(III) Incorrect bank balance might be reflected due to simultaneous withdrawals and deposits,

(IV) If system fails in the middle of a money transfer from one account to another account, it is not possible to establish the consistent state that existed prior to a failure.

Select the correct statement(s) which may provide reasons for the above scenarios.

• (I) occurs due to concurrency control failure.

• (II) occurs due to security enforcement failure.

• (III) occurs due to integrity enforcement failure.

• (IV) occurs due to concurrency control failure.

• (I) occurs due to integrity enforcement failure.

Given below are five major steps that one would perform in setting up a database for a particular enterprise.

(I) Develop a user interface to carry out the task

(II) Define integrity constraints on the data.

(III) Define DDL statements for all appropriate types of data and data relationships.

(IV) Define the conceptual model

What is the correct order of carrying out the steps given above?

• (I) (IV) (III) (II)

• (IV) (III) (II) (I)

• (III) (II) (IV) (I)

• (III) (II) (IV) (I)

• (I) (IV) (II) (III)

Following are the three main steps in designing a new database.

I. Create a logical design that can be expressed in a data model implemented in a commercial DBMS.

II. Requirement Specifications and Analysis.

III. Create the physical design during which, further specifications are provided for storing and accessing database.

Which of the following answers depict the correct order in designing a new database?

• I, II, III

• II, III, I

• I, III, II

• III, I, II

• II, I, III

Which of the following are true with respect to a Database Management System (DBMS)?

• A DBMS is a collection of programmes that enables users to create and maintain a database.

• It is a general purpose software system which facilitates the process of defining, constructing, manipulating and sharing databases among various users and applications.

• DBMS Always Guarantees High Availability and Fault Tolerance

• DBMS Provides Data Security and Access Control

• DBMS Automatically Ensures Data Accuracy and Quality

Which of the following statements are true in a file based data management system?

• Low Overhead

• Robust Data Integrity and Constraints

• Advanced Security Features

• Portability

• Scalability and Complex Querying

The data in a DBMS is described at three levels of abstraction and the database description consists of a schema at each of these three levels of abstraction: the conceptual, physical and external. Which of the following are true with respect to database schema?

• The external schema specifies additional storage details.

• A data definition language (DDL) is used to define the external and conceptual schemas.

• The physical schema summarizes how the relations described in the conceptual schema are actually stored on secondary storage devices such as disks and tapes.

• Each external schema consists of a collection of one or more views and relations from the physical schema.

• External schemas allow data access to be customized at the level of individual users or groups of users.

What does a System Catalog keep track of?

• Data Types: It maintains a list of available data types, including their names, sizes, and allowed values.

• Performance Metrics: It does not store real-time performance metrics, query execution histories, or resource usage statistics.

• Table Definitions: It stores information about tables in the database, including their names, column names, data types, constraints, and indexes.

• Index structure and storage (or Actual Data: The system catalog does not store the actual data records or values)

• Privileges and other security information

Which of the following statements is/are correct in relation to 3 Level ANSI/SPARC

architecture?

• Physical data independence is the ability to change the conceptual schemas without having to change the internal schemas.

• The external level is the user's view of the database and it only contains the relevant data for the user.

• The conceptual level contains and describes what data is stored within the whole database and how the data is interrelated.

• The internal level describes how the data is actually stored in the database.

• Mapping between two levels create an overhead during execution of the query or program.

Which of the following is/are not characteristic(s) of the relational data model?

• Tuple ordering is a part of a relation definition because a relation attempts to represent facts at a logical or abstract level.

• Relational data model enforces data integrity through the use of constraints

• Data is organized into tables (also called relations), where each table consists of rows and columns.

• All the attributes in different relations must have different names.

• A common method of specifying a domain for an attribute is to specify a data type.