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T.Y. Juang Web DBChapter 1 - 1
資料庫系統簡介
臺北大學統計系莊東穎
T.Y. Juang Web DBChapter 1 - 2
Data Hierarchy Hierarchy of Data
– bits
– bytes (characters)
– fields - characters joined together
– records - a collection of related fields
– files - a collection of records
– databases - a collection of linked files
T.Y. Juang Web DBChapter 1 - 3
Data Hierarchy
Bits
Bytes
Fields
Records
Files
Databases
T.Y. Juang Web DBChapter 1 - 4
Definition
Database a collection of data organized in a manner that
allows users to retrieve and use those data an integrated collection of logically related
records and files a collection of information stored in an
organized form in a computer
T.Y. Juang Web DBChapter 1 - 5
Why Database?
– Compactness, Speed, Less Drudgery & Currency• A database consists of some collection of persistent data that is
used by the application systems of some given enterprise– Data Administration
• done by Data Administrator (DA)• a senior management level• decide what data should be stored in the database; establish the
policy of maintaining and dealing with the data (e.g., data security policy)
– Database Administration• done by Database Administrator (DBA)• technical level• create database and control the performance of the system
T.Y. Juang Web DBChapter 1 - 6
Definition
DataBase Management System (DBMS) a software package used to interact with a database a software tool for organizing storage and retrieval of that information a software involves the control of how database are created, interrogated, and maintained to provide information needed by end users and the organization
T.Y. Juang Web DBChapter 1 - 7
Major components of a database systemData: integrated and shared.Hardware: disk, CPU, Main Memory ...Software: DBMSUsers :
1. Application programmers 2. End users 3. Database administrator (DBA)
• Defining conceptual schema• Defining internal schema • Liaising with users • Defining security and integrity checks• Defining backup and recovery procedures • Monitoring performance and changing requirements
T.Y. Juang Web DBChapter 1 - 8
Files and File Management
Payrollprogram
Invoicingprogram
Inventory controlprogram
Payrollfiles
Invoicingfiles
Inventoryfiles
T.Y. Juang Web DBChapter 1 - 9
Databases
Payrollprograms
Invoicingprograms
Inventory controlprograms
DBMS Database
DBMS Database
T.Y. Juang Web DBChapter 1 - 10
Database System Database System Considerations
what information the database will contain? how much access should be given to various
users? how should the database be physically
organized? how can the database structure be made to seem
logical to the user?
T.Y. Juang Web DBChapter 1 - 11
Design Goals Goals
Overcome data redundancy Overcome program dependency on data Allow a large number of users to draw
information easily Link several files for data processing
T.Y. Juang Web DBChapter 1 - 12
Database System ArchitectureHost
Language+ DSL
Host Language
+ DSL
Host Language
+ DSL
Host Language
+ DSL
Host Language
+ DSL
User A1 User A2 User B1 User B2 User B3
External ViewA
External ViewB
External/conceptualmapping A
ConceptualView
External/conceptualmapping B
Conceptual/internalmapping
Stored database (Internal View)
Databasemanagement
system(DBMS)
<
DBA
Storagestructuredefinition(Internalschema)
Conceptualschema
Externalschema
A
Externalschema
B
(Build andmaintainschemas
andmappings)
T.Y. Juang Web DBChapter 1 - 13
Database Models Models (Structures)
a data model describes components of the database and how they work together
a data model describes linking of records that share fields
Common data models Hierarchical Network Relational Object Oriented
T.Y. Juang Web DBChapter 1 - 14
Models
Hierarchical database Network database Relational database
T.Y. Juang Web DBChapter 1 - 15
Hierarchical Data Models
Hierarchical The first conceptual model One-to-many relationship All relationships are established when the database is
created All access is through pre-established links A child can have only one parent IMS, DL/1 (IBM), System 2000(MRI),
METABAS(PMI), MARK IV(INFORMATICS)...
T.Y. Juang Web DBChapter 1 - 16
Network Data Models Network
Like a hierarchical database Can represent more complex logical relationships A child can have more than one parent Parent is called an owner, child is called a member CODASYL(Conference On Data Systems
Languages ) Permits all relationships: one-to-one, one-to-many,
many-to-many DMS-11(Burroughs), DMS-170(CDC),
TOTAL(Cincom), IDMS(Cullinane), DMS1100(Univac)
T.Y. Juang Web DBChapter 1 - 17
Network Data ModelsNetwork
Advantages More flexible than hierarchical database Successfully implemented and marketed
Disadvantages Schema must be defined at time database is created Retrieval of data is based solely on the schema
T.Y. Juang Web DBChapter 1 - 18
Relational Data ModelsRelational
E. F. Codd (1969) Data organized into tables or files called “relations” Tables have - rows, tuples or record
- columns, fields or attributes Range of values for a field is the domain Relationships are determined at time of use Relationships are created by operations on tables Operations are performed at the time of a request No predetermined schema is required
T.Y. Juang Web DBChapter 1 - 19
Relational Data Models Relational
Users can ask virtually any questions Virtually all modern DBMS support these Most popular DB2 (IBM), Oracle (Oracle), SQL Server
(Sybase), INGRES (Computer Associ
ate), INFORMIX OnLine (INFORMIX), M
S SQL Server (MS), Access (MS), ….
T.Y. Juang Web DBChapter 1 - 20
關聯性資料庫管理系統 ( 續 )
stor_id
706670677131804263807896
stor_name
Bamum’sNews & BrewsDoc-U-Mat:Quality Laundry & BooksBookbeatEric the Read BooksFricative Bookshop
city
TustinLos GatosRemuladePortlandSeattleFremont
state
CACAWAORWACA
zip
927899674598014890769805690019
Stores Table
T.Y. Juang Web DBChapter 1 - 21
stor_id
706670677131804263807896
stor_name
Bamum’sNews & BrewsDoc-U-Mat:Quality Laundry & BooksBookbeatEric the Read BooksFricative Bookshop
city
TustinLos GatosRemuladePortlandSeattleFremont
state
CACAWAORWACA
zip
927899674598014890769805690019
Stores Table
Sales Tablestor_id
706670677131713180428042638063808042789678967896804270667131713171317131706770677067
stor_name
QA7442.3D4482N914008N914014423LL922423LL930722a6871P723X999QQ2299TQ456QA879.1A2976P3087aP3087aP3087aP3087aP2121P2121P2121
data
SepSepSepSepSepSepSepSepMarFebOctDecMayMayMayMayMayMayJunJunJun
131414141414131411212812222429292929151515
198519851985198519851985198519851988198819871987198719871987198719871987198719871987
12:AM12:AM12:AM12:AM12:AM12:AM12:AM12:AM12:AM12:AM12:AM12:AM12:AM12:AM12:AM12:AM12:AM12:AM12:AM12:AM12:AM
qty
7510202515103525351510305020251525402020
payterms
On invoiceNet 60Net 30Net 30On invoiceOn invoiceNet 60Net 60Net 30On invoiceNet 60Net 60Net 30Net 30Net 60Net 60Net 60Net 60Net 30Net 30Net 30
title_id
PS2091PS2091PS2091MC3021MC3021BU1032PS2091BU1032BU1111BU2075BU7832MC2222PC1035PC8888PS1372PS2106PS3333PS7777TC3218TC4203TC7777
Discounts Tablestor_id
71318042
discount
6.75.0
T.Y. Juang Web DBChapter 1 - 22
資料具整合性 (Data Integrity)使用結構化查詢語言 (Structured Query
Language) 維護及查詢資料方便性高效率的資料儲存方式安全性
關聯性資料庫管理系統 ( 續 )
T.Y. Juang Web DBChapter 1 - 23
RDBMS 基本功能 Data Definition
Data Manipulation
Data Control Statement
Data Retrieval Data Modification
Data consistencyRecoveryBackup and RestoreSecurityStored ProcedureTriggers
Creating Databases Creating tables
view grant
T.Y. Juang Web DBChapter 1 - 24
Object Oriented Data Model Object Oriented Database
Better handle more complex types of data (graphics, pictures, voice, text) than other database structures
Support encapsulation, inheritance Jasmine (CA) -物件資料庫系統
T.Y. Juang Web DBChapter 1 - 25
Normalization Normalization
– a logical database design involves using formal methods to separate the data into multiple, related tables
– A greater number of narrow tables (with fewer columns) is characteristic of a normalized database
– To improve performance– First Normal Form (1NF), Second Normal Form
(2NF), and Third Normal Form (3NF) and Forth Normal Form (4NF)