school of geography faculty of environment querying with arcgis
TRANSCRIPT
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