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Flashcards in Intro to Database Deck (56)
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1

Why do we need to manage data?

• Organizations could not function long without critical business data
• Cost to replace data would be very high
• Time to reconcile inconsistent data may be too long
• Data often needs to be accessed quickly
• Data should be:
- Cataloged
- Named in standard ways
- Protected
- Accessible to those with a need to know
- Maintained with high quality

2

A collection of data that is organized in a way that facilities retrieval and reporting

Database

3

Uses of Database

• Databases are commonly used to store data which are too large to be managed on a paper or through simple spreadsheets
• Most businesses use databases for accounts, inventory, personnel and other record keeping
• Databases are also becoming more widely used by home users for address books, CD collections, recipe archives, etc.

4

Advantages of Database Approach

• Reduction in data redundancy
• Maintenance of data
• Data are self-documented or self-descriptive
• Avoidance of inconsistencies
• Reduced cost of software development
• Security restrictions

5

Types of Database Software Packages

• File Management System
• Database Management System

6

'flat-file'
records from only one file can be related at a time

File Management System

7

Allow records from multiple files to be related and manipulated at the same time

Database Management System

8

Collection of interrelated data and set of programs to access the data, that provides an environment that is both convenient and efficient to use

Database Management System

9

Database examples

• Customer lists
• Records related to hobbies or collections
• Employee records
• Inventories
• Sales records
• Student grades and information
• Catalogs of tapes or books

10

Levels of abstraction

Physical level
Logical level
View level

11

Describes how a record is stored

Physical level

12

Describes data stored in database and the relationships among the data

Logical level

13

Application programs hide details of data types; views can also hide information for security purposes

View level

14

A way for human to visualize the relationships between records that are filed in complex database management systems

Data Model

15

A collection of tools for describing data, data relationships, data semantics and data constraints

Data Model

16

Types of data model

Hierarchical data model
Network data model
Relational data model
Object-oriented data model

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The oldest data model
Has top-down design; resembles an organizational chart or an inverted tree

Hierarchical data model

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Each record at one level is linked to (or has a parent at) the next level

Hierarchical data model

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Multiple relationships are establish between different braches of the data

Network data model

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The most flexible approach to database organization

Records can be related according to the contents of key fields, or common categories

Relational data model

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The newest data model
They link objects

Object-oriented data model

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Object-based logical models

• Entity-relationship model
• Object-oriented model
• Semantic model
• Functional model

23

Record-based logical models

• Relational model
• Network model
• Hierarchical model

24

A collection of related records that is self-describing

Database file

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All the information that pertains to one person, object or event

Record

26

A required property for each field that defines the type of information that can be entered in each field
The data format that a field value can hold

Data type

27

Data types

Text
Memo
Number
Date/Time
Currency
Autonumber
Yes/No
OLE object
Hyperlink

28

A display of records in a table

Datasheet

29

An independent object that can be related to another in database schema;
May be a person, place, thing, event, organizational grouping, etc.

Entity

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One category of item in a record, such as name, address or a social security number
Aka column names

Field