Basic GIS Tools - Selecting

   


Interactive selection 
These are the simplest selection tools; they allow you to click on features and select them right on the screen.  There are two different tools:
  Select features - click on features and select them, hold down SHIFT or drag a box to select multiple features
   Fence select - same as above, but click to enclose a polygon for selecting


Selectable layers
Both of the above tools will select features from all layers by default.  You can limit which layers are selectable by choosing 'Set Selectable Layers' on the 'Selection' menu:
    
Any layer turned 'off' cannot be selected.  Any layer turned 'on' will be selected.

Selection method
Every selection tool requires a selection method to be specified.  The selection method merely tells ArcMap what to do with previous selections.  There are four choices:
Create new selection - toss out the old selection in favor of the new one
Add to current selection - keep the old selection and add any newly selected features to it
Remove from current selection - keep the old selection but remove any newly selected features from it
Select from current selection - keep only those features which were previously and newly selected

The selection method for the interactive tools described above is set right in the 'Selection' menu under 'Interactive Selection Method':

Select by attributes
This tool is found under the 'Selection' menu in ArcMap.  It allows you to create a selection of features based on their attributes.

It will look something like this:

There is a trick to using this tool, you have to double-click a field name, then single-click an operator, then double-click a value.

Selection layer
Selected features can be saved as a separate layer.  This is a very convenient way to limit a layer to only certain features without having to make redundant data.  Just select the features you want to be in a separate layer and then right-click the layer name to bring up its context menu, go down to the 'Selection' submenu, and choose 'Create Layer from Selected Features':

This will create a new layer in your map document which will consist only of the previously selected features.  It will look like this:

Once a selection layer is made, features cannot be added or removed from the selection - if you need to do this you will have to go and make another selection layer.  Also, the selection layer is only visible in the map document in which it was created, and once removed there is no way to recreate it without redoing the selection.  Finally, the selection layer is a static snapshot of a selection.  If a feature's attributes are changed so that it no longer matches the selection criteria, the selection layer will not automatically update. 

Definition query
Like a selection layer, a definition query limits the features in a layer (in fact, a selection layer is just a type of definition query).  However, a definition query differs in that the query can be changed at any time (thus adding or removing features), and a definition query can only be based on attribute selections.  To create a definition query, right-click the layer name to bring up its context menu, and choose 'Properties'.  This will bring up the layer properties, click on the 'Definition Query' tab.  Here is an example:

Any features which satisfy the definition query are retained in the layer, all others are ignored - from ArcMap's perspective they don't even exist.  You can type a query directly into the box or use the Query Builder, which is the same tool used above for 'Select by Attributes'.