Spatial and Attribute Queries

Data query is one of the main uses of a GIS. Queries can be made based on attributes of the data features (just like you can select cells in Excel spreadsheets or records in non-spatial database packages like Access). Alternatively you can query features based on spatial properties. Examples include:

Using queries is an effective means to manipulate data for subsequent analysis or mapping. Queries can be used to recode items.

With all queries, selections are made based on a currently selected set of features.

In ArcGIS, queries can be made in ArcMap. If the ArcMap session is then saved then the queries are saved (i.e. the next time you open the ArcMap project the queiried sets will persist). Alternatively you can preserve queries by adding a new field to a dataset, perform the desired queries and then setting code values for the new field based on the selected set.

In class example using Montgomery parcels dataset (part of ArcGIS Sample data) highlighting distinction between queries and attributes in vector vs. raster features.