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DDD > CH 1 Databse concepts > Flashcards

CH 1 Databse concepts Flashcards

1
Q

what Is a database?

A

a single large repository of data that is defined once and used simultaneous by many users. e.g many departments.

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2
Q

How is data organized in databases?

A
  • they categorize information into logical groups , which are physically stored in files callled tables.
  • a table is an orderly collection of records
  • a record is a collection of fields
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3
Q

State the properties of a table

A

-Values are atomic . this means that a column in a table should hold only one piece of data
- column values are of the same kind.
- each tuple is distinct; there are no duplicate tuples

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4
Q

what is DBMS?

A

Database Management System.

a software program that controls the organization , storage , management , and retrival of data in a databse. e.g MySql ,PostgreSql

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5
Q

DBMS Functions

A
  • offers data dictionary management
  • offers data storage management
  • offers data intergrity management
  • offers database language and application program interface.
    offers security management
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6
Q

what is data ?

A

Raw facts

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7
Q

field ?

A

a group of characters with a specific meaning

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8
Q

record?

A

Logically connected fields that describe a person, place, or thing

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9
Q

File

A

Collection of related records

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10
Q

File System Critique:

A

evaluating the strengths and weaknesses of different file systems.

It’s about understanding how well a file system performs in various scenarios, and identifying areas where it can be improved.

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11
Q

state a file system data management critique

A
  • requires extensive programming in third-generation language(3gl)
  • time consuming
    makes ad hoc queries impossible
  • leads to islands of information
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12
Q

Data dependece ( file system critique)

A

-Change in file’s data characteristics requires modification of data access programs
-Must tell program what to do and how
-Makes file systems cumbersome from programming and data management views

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13
Q

Stuctural dependence

A

-Change in file structure requires modification of related programs

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14
Q

Field Definitions and Naming Conventions

A

-Flexible record definition anticipates reporting requirements

-Selection of proper field names important

-Attention to length of field names

-Use of unique record identifiers

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15
Q

Data Redudancy

A

-Different and conflicting versions of same data

-Results of uncontrolled data redundancy
*Data anomalies
-Modification
-Insertion
- Deletion
*Data inconsistency
- Lack of data integrity

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16
Q

state the advantages of of databases over file systems.

A

-Eliminates inconsistency, data anomalies, data dependency, and structural dependency problems

-Stores data structures, relationships, and access paths

17
Q

what does a database system Environment consist of?

A
  • People
    *end users *support *databse analyst

-Hardware
*Servers *End devices *network *storage

  • Software
    *DBMS *OS *Programming *Application

-Data

-Procedures
*usage policy *security *data handling *data disposal

18
Q

Database System Type examples

A
  • single-user vs. Multiuser database
    -centralized vs distributed
19
Q

what is a databse Model?

A

its collection of logical contructs used to represent data structure and relationships within the database.

-conceptual models . logic nature of data representation

-implementation models . emphasis on how data are represented in the database.

20
Q

give examples of relationships in conceptual models

A
  • one to many (1:M)
    -one to one(1:1)
    -many to many
21
Q

give examples of implementation databse models

A

-Hierarchial.Logically represented by an upside down tree. each parent can have many children . Each child can have only 1 child.

-netowrk.Each record can have multiple parents.Composed of sets
Each set has owner record and member record

-relational. Perceived by user as a collection of tables for data storage

22
Q

4 advantages of hierarchical Databse Model

A

-conceptual simplicity
- databse security & intergrity
-data independence
-efficiency

23
Q

4 disadvantages of hierarchial database model

A
  • complex implementation
  • difficult to mange and lack of standards
    -lacks structural independence
    applications programming and use complexity
24
Q

4 advantages of network database model

A

-conceptual simlicity
-handles more relationship types.
-promotes databse intergrity
-data independence

25
Q

2 disadvantages of network

A

system complexity
lack of structural independence

26
Q

advantages of relational db model

A

-structural independence
-improved conceptual simplicity
-powerful databse management system.
-Ad hoc query cabability with SQL
- easier database design , implementation , management & use.

27
Q

disadvantages of relational db model

A

-poor design and implementation is made easy.

-may promote “islands of information” problems

-substantial hardware and system software overhead

28
Q

define entity relationship model

A

Complements the relational data model concepts. based on entities , relationships & attributes. represented in erd diagram.

29
Q

er db model advantages

A

-exceptional conceptual simplicity
-visual representation
-effective communication tool
integrated with relational db model

30
Q

disadv of er db model

A

loss of information content
no data manipulation language
limited constraint representation

31
Q

define oo db model

A

Objects or abstractions of real-world entities are stored . attributes describe properties.
-Collection of similar objects is a class
*Methods represent real world
actions of classes
*Classes are organized in a class
hierarchy

32
Q

Advantages of oo data model

A
  • adds semantic content.
  • database integrity
    -both structural and data independence.
    -
33
Q

diadvantages of OO data model

A

-lack of OODM
-complex navigational data access
-steep learning curve
-high system overhead slows transactions.

34
Q

state characteristics of database models and the internet.

A

-Supports complex data types and relationships

-Powerful DBMS GUI make DBA job easier

-Many database design, implementation, and application development tools

-Easily used, developed, and supported

DDD (7 decks)

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