School of GeographyFACULTY OF ENVIRONMENT

Querying with ArcGIS

What is Querying?

• A request to select features or records from a database

• Often written as a statement or logical expression

• Types of queries:

• Interactive

• click on features using the Identify tool

• Find tool

• Distance tool

• Select by Attribute (SQL query)

• Select by Location (spatial query)

• Select by Graphic

Selection Tools

• Select and clear individual features from the Tools toolbar

• Various selection options from the Selection menu

Dynamic Linkage

Selection Options in ArcMap

• Specify interactive selection method + Selection Option (Selection Options)

Select by Attribute

• Uses an SQL where clause to select features

• Save and reload selection expressions

Selected features in blue

Right click in the

Field box

Other Features

• Search on a text name – enclose in single brackets

• Use wildcard characters - % or * for any length; _ for one character in combination with LIKE

• Use Boolean operators to look in more than one column, i.e. AND, OR, NOT, etc.

• Is NULL – to search for null values

• Get Unique Values + Go To:

• Substring (“STATE_NAME”,1,2) = ‘Te’

Select by Location

• Is a spatial query

• Use features in one layer to select features in another

• Examples are to select features in A that are:

• Completely contain B

• Intersect with B

• Are within a specified distance of B

• Are completely within B

• Etc.

Example of a Query by Location

Results of the Query

Addresses within 50m of motorway Further refined to choose only

dwellings

Select by Graphics

• Draw a graphic to select features

• Works with interactive selection methods

Save Selection

Or export

as a shapefile

Data Export Data

Querying in ArcMap

Hands-on Exercise #8