Basic Concepts

Question 1

define database

Answer 1

A collection of related data.

Question 2

data

Answer 2

known facts that can be recorded and have an implicit meaning.

Question 3

mini-world

Answer 3

Some part of the real world about which data is stored in a database. For example, student grades and transcripts at a university.

Question 4

data-base management system (DBMS)

Answer 4

A collection of programs to facilitate the creation and maintenance of a computerized database

Question 5

database system

Answer 5

The DBMS software together with the data itself. Sometimes, the applications are also included

Question 6

A DBMS is a general purpose software system that facilitates the process of ____, ____, and ____ DBs for various applications.

Answer 6

defining, constructing, and manipulating

Question 7

_____ a DB involves specifying the data types, structures and constraints for the data to be stores in the DB.

Answer 7

Defining

Question 8

____ a DB is the process of storing the data itself on some storage medium that is controlled by the DBMS.

Answer 8

Constructing

Question 9

Manipulating a DB involves functions such as ____ the DB to retrieve specific data, ___ the DB to reflect changes in the mini-world, and _____ from the data.

Answer 9

querying; updating; generating reports

Question 10

describe the self-contained nature of database system.

Answer 10

Self-contained nature of database system: A DBMS catalog stores the description of the database. (The description is called meta-data) This allows the DBMS software to work with different databases.

Question 11

The characteristic that allows program-data independence is called _______.

Answer 11

data abstraction Insulation between programs and data: Called program-data independence. Allows changing data storage structures and operations without having to change the DBMS access programs.

Question 12

data model

Answer 12

A set of concepts to describe the structure of a database. A data model is a type of data abstraction that is used to provide the users with a conceptual representation of data that does not include many of the details of how data is stored.

Question 13

Why is multiple views a good characteristic of the database approach?

Answer 13

Support of multiple views of the data: Each user may see a different view of the database, which describes only the data of interest to that user.

Question 14

concurrency control w.r.t. DBMS

Answer 14

The DBMS must include concurrency control software to ensure that multiple users trying to update the same data do so in a controlled manner so that the result of the update is correct.

Question 15

List four groups of people who might interact with a database

Answer 15

database administrators database designers end users system analysts and application programmers

Question 16

When not to use a DBMS

Answer 16

• If the database and applications are simple, well defined, and not expected to change.
• If there are stringent real time requirements that may not be met because of DBMS overhead.
• If access to data by multiple users is not required. Sometimes no DBMS may suffice:
• If the database system is not able to handle the complexity of data because of modeling limitations.

Question 17

The ____ of a database refers to the data types, relationships, and constraints that the database should obey.

Answer 17

structure

Question 18

A data model can also contain _______ that specify database retrievals and updates by referring to the concepts of the data model.

Answer 18

user-defined operations

Question 19

Name 3 Categories of data models

Answer 19

conceptual, physical, and implementation

Question 20

conceptual data models

Answer 20

high-level, semantic data models; provide concepts that are close to the way many users perceive data. Also called entity-based or object-based data models.

Question 21

physical data models

Answer 21

low-level, internal data models; provide concepts that describe details how how data is stored in the computer.

Question 22

implementation

Answer 22

record-oriented data models; Provide concepts that fall between conceptual and physical data models, balancing user views with some computer storage details.

Question 23

database schema

Answer 23

The description of a database. Includes descriptions of the database structure and the constraints that should hold on the database.

Question 24

schema diagram

Answer 24

A diagrammatic display of some aspect of a database system.

Question 25

database instance

Answer 25

The actual data stored in a database at a particular moment in time. Also called database state (or occurence).

Question 26

The database schema changes very \_\_\_\_\_\_. The database state changes \_\_\_\_\_\_\_\_\_\_.

Answer 26

infrequently; every time the database is updated

Question 27

Schema is also called

Answer 27

intension

Question 28

State, or instance, is sometimes called

Answer 28

extension

Question 29

What are the three levels of the three level architecture?

Answer 29

internal schema, conceptual schema, external schema

Question 30

What characteristics of the database approach is the three level architecture proposed to support?

Answer 30

program-data independence and multiple views of the data.

Question 31

Internal schema

Answer 31

the internal level to describe data storage structures and access paths. Typically uses a physical data model.

Question 32

Conceptual schema

Answer 32

at the conceptual level to descrive the structure and constrains for the whole database. Uses a conceptual or an implementation data model.

Question 33

External schemas

Answer 33

at the external level to descrive the various user views. Usually uses the same data model as the conceptual level.

Question 34

\_\_\_\_\_ among schema levels are also needed.

Answer 34

Mappings. Programs refer to an external schema, and are mapped by the DBMS to the interal schema for execution.

Question 35

logical data independence vs. physical data indepence

Answer 35

**logical data independence** is the capacity to change the conceptual schema without having to change the external schemas and their application programs. **physical data independence** is the capacity to change the inernal schema without having to change the coneptual schema.

Question 36

When a schema at a lower level is changed, only the mappings between this schema and higher-level schemas need to be changed in a DBMS that fully supports data independece. The higher level schemas themselves are \_\_\_\_\_.

Answer 36

unchanged; Hence, the application programs need not be changed since they refer to the external shemas

Question 37

data definition language

Answer 37

Used by the DBA and database designers to specify the conceptual schema of a database.

Question 38

In many DBMSs, the DDL is also used to define _____ and _____ schemas(views)

Answer 38

internal and external

Question 39

In some DBMSs, separate ________ and _________ are used to define internal and external schemas respectively.

Answer 39

storage definition language (SDL) and view definition language (VDL)

Question 40

data manipulation language (DML)

Answer 40

Used to specify database retrievals and updates.

Question 41

In current DBMS a _________ is used that includes constructs for conceptual schema definiton, view definition, and schema, and data manipulation.

Answer 41

comprehensive integrated language

Question 42

DML commands (data sublanguage) can be embedded in a general-purpose programmign language (host language), such as COBOL, PL/1 or PASCAL. Alternatively, stand alone DML commands can be applied directly (query language). A DML that can be used on its own to specify complex DB operations in a conside manner is called \_\_\_\_\_\_\_\_\_\_\_.

Answer 42

high-level DML (as oppose to a low-level DML)

Question 43

A ________ DML can specify and retrieve many records in a single DML statement (\_\_\_\_\_\_\_ DML). A low-level DML retrieves and process each time one record from a set of records (\_\_\_\_\_\_\_ DML)

Answer 43

high-level; set-at-a-time; record-at-a-time

Question 44

A query in a high-level DML often specifies which data to retrieve (\_\_\_\_\_\_\_\_) rather than how to retrieve it (\_\_\_\_\_\_\_\_)

Answer 44

declarative; procedural language

Question 45

The ____________ is used to store schema decriptions and other information such as design decisions, application program descriptions, user information, usage standards, etc.

Answer 45

data dictionary / repository

Question 46

object data mdoel

Answer 46

The Object data model defines a database in terms of objects, their properties, and their operations. Objects belong to classes; classes are organzied into hierarchies; the operations of each class are specified in terms of predefined procedures called methods.

Question 47

network data model

Answer 47

The Network data model represents data as record types and 1:N relationships (called set types). It has an associated record-at-a-time language that must be embedded in a host programming language.

Question 48

hierarchical data model

Answer 48

The Hierarchical data model represents data as hierarchical tree structures (parent-child relationship types) There is no standard language. Most hierarchical DBMS use a record-at-a-time language.