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Intro to GIS | Summer 2012 Attribute Tables – Part 1

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Intro to GIS | Summer 2012 Attribute Tables – Part 1. DATABASES. Why do we care about Databases?. Integrated sets of data Focused on a particular area and subject Form the basis of GIS analysis and decision-making

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slide1

Intro to GIS | Summer 2012

Attribute Tables – Part 1

slide3

Why do we care about Databases?

  • Integrated sets of data
  • Focused on a particular area and subject
  • Form the basis of GIS analysis and decision-making
  • Must be well-structured in order for us to best access the information stored in them
slide4

How are Databases Managed?

  • Database Management System (DBMS) = system or software program(s) that enables you to store, modify and extract information from a database
slide5

Relational Database (RDBMS)

  • Supports the representation of data as a set of tables that are related to each other
  • Each table = a list of records containing attributes about features
  • Tied together by a “Attribute Key” = an attribute field common to both tables
slide6

Table Data Structure

Record: a row in a database; represents one feature (a.k.a. “tuple”)

Attribute: a column in a database; contains attribute values (a.k.a. “field”)

slide10

Object (ODBMS) & Object-Relational (ORDBMS) Databases

  • ODBMS = Supports the representation of data as objects having attributes, methods and behavior
    • e.g. ArcGIS geodatabases
  • Designed to address the weaknesses of RDBMS such as:
    • Geometry and attribute data are stored in separate databases
    • Poor performance for many types of geographic query
  • Geographic extensions to standard RDBMS can provide similar functionality (ORDBMS)
slide12

What is a Geographic (Spatial) Database?

  • Contains one or more tables with a geographic component (a “shape” attribute)
  • Common example: an ESRI Geodatabase
esri geodatabase
Features can be:

Constrained (domains)

Validated by rules

Modeled with complex behavior

ESRI Geodatabase

Features have:

  • Shapes
  • Attributes
  • Spatial Reference
  • Relationships
types of geodatabases
Types of Geodatabases

Personal

  • Single-user
  • Microsoft Access
  • Up to 2 GB storage

File

  • Single-user
  • File folder structure
  • Up to 1 TB storage

ArcSDE

  • Multi-User, supports versioning
  • Oracle, Microsoft SQL Server, IBM DB2, IBM Informix, PostgreSQL
  • Storage limit based on DBMS type

ESRI Comparison of Geodatabases

default geodatabase
“Default” Geodatabase
  • A setting in ArcGIS
  • Helps with data management
  • Allows you to:
    • Store all datasets in one convenient location, or
    • Set a database for each project
slide21

Getting Information from GIS data

  • Query = to question or inquire about a feature(s) shown on a map (and by extension, in a GIS dataset)
  • Output is a selected set of records
  • Two approaches:
      • Attribute queries
      • Spatial queries
slide22

Attribute Queries

  • Selects features based on non-spatial information in an attribute table
    • e.g. Which counties in the US have > 100,000 people?
  • “Select By Attributes” tool in ArcMap
  • SQL (structured query language) used to write query
slide25

Spatial Queries

  • Selects features based on location or spatial relationship between data layers
        • e.g. Which Oregon counties have an interstate highway passing through them?
  • “Select Layer by Location” tool in ArcMap
    • Target layer = base layer; contains features you want selected
    • Filter layer = comparison layer
  • What kind of spatial relationships are possible between points, lines and polygons?
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