©2007 by austin troy. all rights reserved lecture 6 database concepts introduction to gis by brian...

©2007 by Austin Troy. All rights reserved

Lecture 6

Database Concepts

Introduction to GIS

By Brian VoigtUniversity of Vermont

Thanks are due to Dr Troy, upon whose lecture much of this material is based.

Fundamentals of GIS

Lecture slides by Austin Troy & Brian Voigt, University of Vermont, © 2011

People• typically use a decimal (base 10) number system• each digit corresponds to 10 to some power• a number with 3 digits has 103 or 1000 possibilities

Computers• use a base 2 system … a bit (Binary digIT) has 2

possible values• a byte is 8 “on-off switches” or bits • each switch/bit represents a binary number• one byte is 28 or 256 possibilities

How is Data Stored?


Example: 12,345 (base 10)

1*10,000 + 2*1,000 + 3*100 + 4*10 + 5*1

1*104 + 2*103 + 3*102 + 4*101 + 5*100

Introduction to GIS

How is Data Stored?


• Switch combinations determine decimal number based on the formula:

• N10= 2b-1+2b-2+…2b-b

• Where b= number of bits storing the number• Hence the binary number

111111112 = 27*1+ 26 *1 + 25 *1 + 24 *1 + 23 *1

+22 *1 + 21 *1 + 20 *1 = 25510

111111102 = 27*1+ 26 *1 + 25 *1 + 24 *1 + 23 *1 +22 1 + 21 *1 + 20 *0 = 25410

Introduction to GIS

How do binary numbers translate to real numbers?


• Number of possible values for a unit of data is an exponential function of the number of switches • 28 = 256 eight bit data• 216 = 65,536 sixteen bit data• 232 = 4,294,967,296 thirty two bit data

Introduction to GIS

Number of Possible Values


Introduction to GIS


Number of bits determines data types

Examples of Integer data types Byte: 28 (0 to 255) Short Integer: 216 (ranges from –32,767 to +32,767 without decimals, the sixteenth bit determines sign) Long Integer: 232 (+/-2.147483648e+09 )

Floating point: precision can go to either side of decimal place

Single precision: 32 bit Double precision: 64 bit

Introduction to GIS


Currency

Date (recognizes order in dates)

String (text)

When numbers are represented as text they

have no numerical properties (e.g. zip codes)

Boolean (TRUE/FALSE ; yes/no)

Object (“BLOB”, e.g., image file)

Introduction to GIS

Other Data Types


Three Classic Database Models

• Hierarchical

• Network

• Relational - ArcView and ArcInfo use this model

Introduction to GIS


Hierarchical Database ModelA one-to-many method for storing data in a database that

looks like a family tree with one root and a number of branches or subdivisions. Problem: table linkages must be known in advance

Introduction to GIS

Groovy 70s TV

Action shows Drama Sitcoms

Dukes of Hazzard CHIPs

Dallas Fantasy Island

Love Boat Starsky and Hutch

Tom Wopat

Eric Estrada

Gavin McLeodLarry

Wilcox

Larry Hagman Ricardo

Montalban

David Soul

Ted Lange


Hierarchical Database Model

Introduction to GIS

Example where this model works well:

• Taxonomies• Soil classification

Works when: classes are totally mutually exclusive / exhaustive


Hierarchical Database Model

Introduction to GIS

Problem:• Does not work when there are entities that belong to several classes or do not have mutual exclusivity• Think about the problems with Windows Explorer• Example: classifying your music collection


Networked Database Model

A database design for storing information by linking all records that are related with a list of “pointers.” Problem: linkages in the tables must be known before. Not adaptable to change.

Introduction to GIS

Action shows Drama Sitcoms

Dukes of Hazzard CHIPs

Dallas Fantasy Island

Love Boat Three’s company

ABCCBSNBC


Relational (Tabular) Database Model

A design used in database systems in which relationships are created between one or more flat files or tables based on the ideathat each pair of tables has a field in common, or “key”. In a relational database, the records are generally different in each table

The advantages: each table can be prepared and maintained separately, tables can remain separate until a query requires connecting, or relating them, relationships can be one to one, one to many, or many to one

Introduction to GIS


Introduction to GIS

Name Phone Address Student ID

*** *** *** ***

*** *** *** ***

*** *** *** ***

*** *** *** ***

*** *** *** ***

• Headings are the labels for the columns

• Fields, or columns, are attribute categories

• Records, or rows, are the unit that the data are specific to

• Cells are where individual values of a record for a field are stored

Data Tables (flat files)

RECORD

FIELD

CELL


Introduction to GIS

Course name

Course number

enrollment faculty ID

*** *** *** ***

*** *** *** ***

*** *** *** ***

*** *** *** ***

*** *** *** ***

The key is a field that is common to two or more flat files; allows a query to be done across multiple tables or allows two tables to be joined

Data key

Name Phone Address faculty ID

*** *** *** ***

*** *** *** ***

*** *** *** ***

*** *** *** ***

*** *** *** ***

Flat file: professor info Flat file: course info


• Based on the values of a field that can be found in both tables• The name of the field does not have to be the same• The data type has to be the same• In this case we have a one to one join; here the key is unique

Key A B

1

2

3

ID C

1

2

1

2

3

4

5

6

10

20Key A B

1

2

3

1

2

3

4

5

6

C

10

10

50JOIN

Introduction to GIS

3 50Table 1

Table 2

Joining Tables

Joined Table


Join Tables

Key A B

1

1

2

Key C

1

2

1

2

3

4

5

6

10

20Key A B

1

1

2

1

2

3

4

5

6

C

10

10

20JOIN

Introduction to GIS

In this case we have a one to many join; here the key is not unique


Relational (Tabular) Database Model: 70s TV exampleNow we can have various flat files (tables) with different record types and with various attributes specific to each record

Introduction to GIS

Actor Year born*

Sideburn length

David Soul 1948 serious

Eric Estrada 1949 moderate

Larry Wilcox

1953 slight

Tom Wopat 1950 major

Show Lead actor

Co-star Network*

Starsky and Hutch

David Soul

Paul Michael Glaser

ABC

CHIPs Eric Estrada

Larry Wilcox CBS

Dukes Tom Wopat

John Schneider

NBC

*entirely guessed at- I am not responsible for mistaken TV trivia

Table 1- specific to actors

Table 2- specific to shows


Relational (Tabular) Database ModelThis allows queries that go across tables, like which CBS lead actors were born before 1951? Answer: Tom Wopat and David Sole

Introduction to GIS

Actor Year born*

Sideburn length

David Sole 1948 serious


Larry Wilcox

1953 slight


Show Lead actor

Co-star Network*

Starsky and Hutch

David Soul

Paul Michael Glaser

CBS

CHIPs Eric Estrada

Larry Wilcox ABC

Dukes Tom Wopat

John Schneider

CBS

*entirely guessed at- I am not responsible for mistaken TV trivia

It does this by combining information from the two tables, using common key fields


Relational (Tabular) Database ModelObject-relational databases can contain other objects as well, like images, video clips, executable files, sounds, links

Introduction to GIS

Actor Year born*

Sideburn length

Picture

David Soul 1948 serious


Larry Wilcox

1953 slight



Relational Database: another example: property lot info

Introduction to GIS

One-to-one relationship

Parcel ID

Street address

zoning

11 15 Maple St.

Residential-1

12 85 Brooks Ave

Commercial-2

13 74 Windam Ct.

Residential 4Owner Parcel ID occupation

J. Smith

13 lawyer

R. Jones

11 dentist

T. Flores

12 Real estate developer


Relational database: one to many relationship

Introduction to GIS

One-to-many relationship

Parcel ID

Street address

zoning

11 15 Maple St.

Residential-1

12 85 Brooks Ave

Commercial-2

13 74 Windam Ct.

Residential 4

Owner Parcel ID occupation

J. Smith 13 lawyer

R. Jones 11 dentist

J. McCann

12 financier

T. Flores

12 Real estate developer

In this case, several people co-own the same lot, so no longer one lot, one person


Assuming each owner owned several parcels, we would structure the database differently

Introduction to GIS

One-to-many relationshipParcel

IDStreet address

zoning

11 15 Maple St. Residential-1

12 85 Brooks Ave Commercial-2

13 74 Windam Ct. Residential 4

Owner occupation # properties owned

J. Smith lawyer 2

R. Jones dentist 5

J. McCann financier 2

T. Flores Real estate developer

3

Properties owned by T. Flores

Owner Parcel ID

Date of transaction

Flores 13 4-15-00

Flores 15 4-17-01

Flores 19 3-12-99

Note: this table includes data pertinent only to Flores’ ownership of these properties


ExampleHere’s an example of a chart showing the relationships between flat files in a sample relational database for food suppliers* in Microsoft Access

Introduction to GIS

* This comes from an MS ACCESS sample database


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Introduction to GIS


A real time RDBMS allows for realtime linking and embedding of tables based on common fields

Here we see all the orders for product ID 3; there is no need to include product ID in that sub-table


DEMO

Working with other number systems

©2007 by austin troy. all rights reserved lecture 6 database concepts introduction to gis by brian...

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