database management system (dbms) by: dr. mohamed yagoub mohamed e-mail: [email protected] url:

Database Management System (DBMS)

By: Dr. Mohamed Yagoub Mohamed

E-mail: [email protected]

URL: http://www.angelfire.com/mo/yagoub

OverviewOverview

Why we need database

Database Concept

Types of database models

Relational database

DBMS

• DBMS is a collection of data (database) and programs to access that data. The goal of DBMS is to store, retrieve, and display information

• Key characteristics of DBMS are: performance, store large volume of database, share data (access), provide security (authorization), remove redundancy (normalization) and provide concurrent access (different users at the same time).

Why we need database?

Without database GIS is cartography

(electronic map)

No database No spatial analysis

Why we need database?

Principles of GIS

GIS

Hardware

Software

Information

People

Database and GIS

Spatial datalocation

AttributeDBMS

GIS database

Text, ImagesSound, movieMultimedia

Data abstraction

• Physical level: Describe how the data are actually store (word or bytes)

• Conceptual level: Describe what data are actually stored in the database (Structure). it gives Schematic representation of phenomena

• View level: Describe only a part of the entire database. Many users of the database may be concerned with a subset of information. The system may provide many views for the same database

Data abstraction-Continue

Conceptual level

Logical Level

Different users for the same database

Data abstraction

View Level

Instance of schemes

• The collection of database at a particular moment is called the instance of the database

• The overall design of the database is called the database scheme

Types of database models

Data model is a collection of conceptual tools for describing data, data relationship, data semantics, and consistency constraints. There are mainly three types of models

• Object-based logical models Are used to describe data at the

conceptual and view level. Example of these the Entity-Relationship model and object-oriented model

Data models- Continue

• Record-based logical models Are used to describe data at the conceptual and

view level. Example of these are: Network model, Hierarchical model, and relational model.

• Physical data models Are used to describe data at the physical level

(bytes and words). It is mainly deal with hardware.

Entity-Relationship (E-R) model

• It is based on simulation of the real world which consists of basic objects called entities and relationship among these objects

• The overall logical data structure of a database can be expressed graphically by an E-R diagram. Which consists of rectangle (entity), ellipse (attribute), diamond(relationship), and lines.

E-R Diagram for customer CustomAcct relationship associate a customer with each account he has

Customer

Street

NameSSN

Account

NumberBalance

CustomAcct

Date

3 Tables can represent the above relation

12

3

Aggregation

Aggregation is an abstraction through which relationships are treated as higher-level entities i.e. express relationships among relationships

Users

ProjectEmployee Work

Name SSN Number

Hours

Type

Machinery

E-R diagram with aggregation

5 tables canrepresent thediagram

Generalization

In E-R diagram generalization is depicted through a triangle labeled ISA (is a). The attribute of higher level entity are said to be inherited by lower level entity. e.g. both saving and checking account inherit the attributes of account

Balance

Account

Interest rateOver draft

Checking accountSaving account

ISA

Account number

E-R diagram with generalization

3 tables canrepresent thediagram

E-R diagram Table

• An Entity (E) with attributes a1..an can be represented by a table called E with n columns for each attribute.

• Each row in this table corresponds to one entity of the entity set E

Let D1 ==> set of all account number

D2===> set of all balance

Any row consists of 2 tuples (v1,v2) e.g. (255,3000)

The set of all possible rows is the Cartesian product of D1 and D2 i.e. = D1 X D2

For a table with n columns the

total number of rows = D1 X D2 X ..X Dn-1 X Dn

255

560

215

3000Account_no

452

323

balance

32223455521000

456780

Mapping constraints

• Mapping cardinalities express the number of entities to which another entity can be associated via a relationship

• For a binary relationship set R between entity set A and B the mapping can be one-one (1-1), one-many(1-M), many-one (M-1), and many-many(M-M)

a1a2

b1b2b3

1-M relation

Object oriented Model

The basic unit that an object-oriented (OO-DBMS)

manages is the object. It is based on four basic

concepts of abstraction:

• Classification: Mapping of several objects

(instances) to common class

• Generalization: Group several classes which

have the same properties in common (roads,

railway)-transportation network

Object oriented Model-Continue

• Association: Relation between similar

objects is considered a higher level set

object

• Aggregation: Objects which consist of

several other objects (Composed objects)

Object oriented Model-Continue• OO model uses objects rather than records to manage data

• An object is a collection of data elements and operations

that together are considered a single entity

• An object has associated with it a set of variables that

contain the data for the object, a set of messages to which

the object respond, and a method which response to the

message

Object Oriented Model-Continue

• Once the structure is setup, the details of it

need not be user visible

• This approach has the attraction that query is

very natural

• A geographic data handling systems employ

this model are:

TIGRIS, DAPLEX, and PROBE

• It is application in GIS is recommended


• Objects are typed and the format and

operations of an object instance are the same

as some object prototype

• Example of an object might be a lake:• List of border chain: C1, C2, C3, Cn

• List of nodes: N1, N2, N3, Nn

• Attribute: Depth, soil type


For example student can be a superclass. First and secondyear student may represented by a classes that are specialization of a student class variables and methods specific to first year students are associated with fist year student class.Variables and methods that apply both to first and second year students are associated with student class.The variables associated with each class may be:Student: Name, ID, addressFirst year student: Subject Second year student:Practical course

Student

First year Second year

Hierarchical Model

• Based on Tree structure (child-parent)

• No element can have more than one parent

• Requires knowledge by the user of the

actual storage scheme used by the DBMS

• Examples of database are:

System2000 and IMS

• Not commonly applicable in GIS

Network Model

• Organized data in a network or plex

structure (child-parent)

• Children may have more than one parent

• The query language is procedural

• Examples of database are:

DBMS-10, DMS1100, IDMS

• Not commonly applicable in GIS

A1

B1 B2

C1 C2 C3C4 C5 C6

Root (Parent)

ChildParent

ChildChild

Database tree structure (Hierarchical, Network)

Relational model• A relational database consists of a collection of

tables, each of which is assigned a unique name• The relational models differs from network and

hierarchical models in that it does not use pointers or links. Instead , the relational model relate records by the value they contain.This freedom from the use of pointers allows formal mathematical foundation to be defined

• Examples of RDBMS are Oracle, Informix, and Sybase

Reasons to use Relational Model• Independence of the physical data storage and logical

database structure. Results in users do not need to understand the underlying physical layout of the data to access data from a logical structure, such as a table

• Variable and easy access to all data. Results in access to data is not predefined as in hierarchical databases in which users must understand and navigate through the hierarchy to retrieve data

• Flexible in database design. i.e complex objects are expressed as simple tables and relationships

• Applying relational design methods reduces data redundancy (Normalization) and storage requirements

Relational DBMS

• Aspects of an RDBMS

– Structures: Well defined objects– Operations: Clearly defined actions– Integrity Rules: Rules that control which

operations are allowed on the data and structures of the database

Relational DBMS

• Components of a Relational Database– Table: collection of rows all containing the

same columns– Row: Horizontal components of a table.

Consists of values for each column. Each row is equivalent to a record

– Column: Vertical component of a table. Each column in the record is often referred to as a field

Relational DBMS

• Relational Database Rules– Each column in a table must be unique– The order of the rows in a table is not meaningful– The order of the columns in a table is not

meaningful– All data in a column must be the same type– Every table has a primary key, each column in the

primary key must have a value

Relational DBMS

• Primary Key and Foreign Key– Relational database use primary keys and

foreign keys to allow mapping of information from one table to another

– A foreign key is column or group of columns in a table whose value matches those of the primary key of another table

– Values in primary key column must be unique e.g. social security number (SSN)

Relational DBMS

• Primary Key and Foreign Key– Referential Integrity refers to the integrity of

the reference from the primary key in one table to a foreign key in another table.

Relationships between Tables

• One-to-One

• One-to-Many

• Many-to-One

• Many-to-Many

Relational DBMS

• Relational Database Example (1-1)

05-01-94 70

Weather table

Location table

Washington

Seattlecity_name

AmsterdamWarsawTokyo

Washington

country_nameUnited StatesNeatherlands

PolandJapan

05-01-94Primary KeyForeign Key

Primary Key

city_name

AmsterdamWarsawTokyo

Washington

measurement_dt

05-01-9405-01-9405-01-9405-01-94

avg_temp

47436055

One-to-One

NAME AREA POP1990

Caroline 331.8066 27035Talbot 238.2847 30549Dorchester 534.1747 30236Wicomico 383.3481 74339Worcester 457.6503 35028Somerset 269.267 23440

NAME POP1997

Caroline 29424Talbot 32565Dorchester 29953Wicomico 79716Worcester 41885Somerset 24251

NAME AREA POP1990 POP1997

Caroline 331.8066 27035 29424Talbot 238.2847 30549 32565Dorchester 534.1747 30236 29953Wicomico 383.3481 74339 79716Worcester 457.6503 35028 41885Somerset 269.267 23440 24251

Relational DBMS

• Relational Database Example (1-M)

comp_nameKotrayaH.PlazaKomtar

N.Shops444555622

N.Banks704743

Complexes table

comp_nameKotraya

Kotraya Kotraya Kotraya

shop_ownerALiTanLee

RamanNora

Owner table

Foreign Key

Primary Key

Kotraya

One-to-Many

Dept. Advisor

Agri ShorterAgri MollettNat Sci Ruby

Advisor Name

Shorter AaronRuby BrianMollett DevinShorter EricShorter JulieRuby Leigh

Mollett RonnieMollett Ryan

Dept. Advisor Name

Agri Shorter AaronNat Sci Ruby BrianAgri Mollett DevinAgri Shorter EricAgri Shorter JulieNat Sci Ruby Leigh

Agri Mollett RonnieAgri Mollett Ryan

Many-to-One

SITE AREA Veg Type

WV1 331.8066 D1WV2 238.2847 C2MD1 534.1747 D1MD2 383.3481 S3

Veg Type Name Dominant pH of Soil

C2 Forest Coniferous Scrub Pine 6.5D1 Forest Deciduous Maple 8S3 Wetland Swamp Skunk Cabbage 5

SITE AREA Veg Type Name Dominant pH of Soil

WV1 331.8066 D1 Forest Deciduous Maple 8WV2 238.2847 C2 Forest Coniferous Scrub Pine 6.5MD1 534.1747 D1 Forest Deciduous Maple 8MD2 383.3481 S3 Wetland Swamp Skunk Cabbage 5

Data Definition Language (DDL)and Data Manipulation Language (DML)

• DDL store files that contains data about data (metadata). For example storage of structure in data dictionary

• DML enable users to access or manipulate data (retrieval, insertion, deletion). The part of DML that involves information retrieval is called a query language (QL)

Types of DML

• There are two types of DML, procedural and non procedural

• Procedural DML: Require the user to specify what data is needed and how to get it

• Non-procedural DML: Require the user to specify what data is needed without specify how to get it

Query language (QL)

• QL is the language in which a user requests information from the database. Example of QL are relational algebra (procedural) and tuple relational calculus (nonprocedural)

• The most common query languages are Structured Query Language (SQL),Query By Example (QBE), and Quel

• SQL has gain wide acceptance in commercial products

Relational algebra (RA)

• RA is a procedural query language. It consists of a set of operations that take one or two relations as input and produce a new relation as a result

• The fundamental operations in RA are select(6), project(II), Cartesian product(X) , rename, union(U), and set difference(-)

• Other operations include intersection, natural join, division, and assignment

• To select those tuples (rows) of the AccCust relation where customer name is “John” it could be written as:

6name = “John” (AccCust)

The results may be one or more records

or street = “ spring”

6street = “Spring” (AccCust)

• Comparisons can done using =, >, <, >=,etc.

• Let E1 and E2 be relational algebra expressions. Then the following are all relational algebra expressions:

• E1 U E2 union

• E1 - E2 set difference(-)

• E1 X E2 Cartesian product

Structured Query Language (SQL)

• SQL is the standard relational database language

• SQL include commands not only restricted to query but to other functions such as defining relation, deleting relations, creating indices, and modifying relation scheme, access right, integrity, and transaction control

• Basic structure of an SQL expression consists of three clauses: Select, from, and where

• A typical SQL query has the formselect A1, A2, ..., An

from r1, r2, .., rm where P

Each Ai represents an attribute and each ri a relation. P is a predicate (selection). The list of attributes A1..An can be replaced by (*) to select all attributes

• The result of an SQL query is a relation (table)

• The keyword “distinct” is used after select to force the elimination of duplicates. For example, find all customer names having a balance equal $ 6000

select distinct customer-name from AccCust where balance = 6000

• SQL supports union, intersect, and minus

• SQL uses logical connectives and, or, and not and operators (+, -, *, /) on values from tuples

e.g.

select distinct customer-name from AccCust

where balance between 600 and 700

• Typical Roles and Privileges

Setting up User Accounts and Privileges

User 1 User 2

create table create view alter table select update

User 3 User 4

Role 1

– In a relational database, data is stored in tables– Users with connect privileges can create tables– The creator of the table becomes the owner– Users cannot access the tables unless

permission is explicitly given– Users can modify the database by deletion i.e.

remove selected tuples, insertion i.e. insert tuples, or update i.e change a value in a tuple without changing all values in the tuple

Creating Tables

Field types

• INTEGERS e.g. number of population, age• REAL (DECIMAL) e.g. income, salary• CHARACTER e.g. names, description • DATES e.g. date of flood• IMAGES (Multimedia) e.g. image of flood

(*.tif) • SOUND e.g. Sound of thunder (*.wav)• MOVIE e.g. recording film (*.avi, *.mov)

• Granting Object Privileges– Only owners of a database object can grant

object privileges to other users– Only users with DBA privileges can grant

object privileges to roles

• Indexes are optional structures that can be created on any column or set of columns in a table to speed up viewing and retrieval of data rows.

• An index is a list of keywords with the location of the keyword information

• Users can create indexes

Creating and Displaying Indexes

– Index is conceptually similar to an index at the end of a book or cataloging books in a library

– Database index is not a physical structure but a logical structure. The RDBMS, not the user uses the database index. The DBMS chooses the best index to use in the table.

– Index can dramatically speed up data access but will require additional space and may slow down certain SQL operations

Index Concept

• Export and Import utilities allows data to be moved in and out of the native database. For Example, converting database tables to other format such Comma Delimited Format (CDF), Space Delimited Format (SDF), *.dbf, and ASCII flat files (Text)

Exporting and Importing Data

Relational Database design

In the database design considerations must be paid to:

• Repetition of information (Normalization)

• Loss of information

• Number of fields and records required, some RDBMS supports limited number of fields and records (e.g. 255 fields)

• Nature of database, some RDMBS supports only textual data, some supports multimedia (sound, image, etc.)

Database quality

Check accuracy of attribute database by Performing quality assurance / quality control (QA/QC) on the database by:

• Check correctness of data

• Check mis-typing errors

Storage Capacity Terminology

NCGIA

Symbol Term Bytes Actual Bytes

K Kilobyte 1000 1024

M Megabyte 1,000,000 1,048,576

G Gigabyte 1,000,000,000 1,073,741,824

Boolean expressions

• AND

• OR

• NOT

AND

A AND B = ResultT T TT F FF T FF F F

Boolean Operatorsboth expressions are true

Elevation >= 100 AND Veg Type = conif

Elevation Veg Type Rainfall pH

100 Mixed 1 7.0250 conif 3 6.550 conif 2 4.0225 decid 1 8.0

OR

A OR B = ResultT T TT F TF T TF F F

Boolean Operatorsat least one expression is true

Rainfall > 2 OR Veg type = decid



NOT

Negates the Boolean value.

Returns TRUE if the Boolean is FALSE

Returns FALSE if the Boolean is TRUE

Boolean OperatorsExcludes informationNOT pH <= 6.5



Operators

- equals

- greater than

- less than

- not equal to

Operators

- greater than or equal to

- less than or equal to

- expressions enclosed in

parentheses are evaluated first

Query Syntax

[ ] around field names

_ in place of spaces in field names

“ ” around string values

( ) grouping and evaluation order

* multiple character wildcard

? Single character wildcard

Date format yyyymmdd

Query Syntax Examples

([Roof_type] = "tile”)([Owner_age] > 65 and [Income] < 20000 )([Type_use] = "res*" and [Const_date] < 1955)([State_name] = “A*”)([Name] = “?athy”)([Date] = 19991027)

Common Query Syntax Errors

[Roof_type] = "tile”)

([Owner_age] > 65) and [Income] < 20000 )

([Type_use] = res*)

([Const_date] < “1955”)

Query SyntaxSalisbury Princess AnneHebron Willards

Correct Query Syntax

([City] = “Salisbury” OR [City] = “Princess Anne” OR [City] = “Hebron” OR [City] = “Willards”)

Incorrect Query Syntax

([City] = “Salisbury” OR “Princess Anne” OR “Hebron” OR “Willards”)

References

• Bailey, T. C. (1994). “A review of statistical spatial analysis in geographical information systems.” In: Fotheringham, A. S. and P. A. Rogerson (eds.). Spatial analysis and GIS. Taylor & Francis Ltd., London, UK.

• Batini, C. S. and S. B. Navathe (1992). Conceptual database design. The Benjamin/ Cummings Publishing, California, USA.

• Hoffer, J. A., J. S. Valacich and J. F. George (1996). Modern systems analysis and design. The Benjamin/Cummings Publishing, California, USA.

• Michael, A. and C. Smith (1996). Teach yourself database programming with Visual Basic 4 in 21 days. Sams Publishing, Indiana, USA

database management system (dbms) by: dr. mohamed yagoub mohamed e-mail: [email protected] url:

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