Querying Data in ArcMap

Identifying, Selecting, and Finding Features:

There are many ways to retrieve information about features in ArcMap™. The user can identify features by clicking on them in order to display their attributes. The user can select features by clicking on the features to highlight them and look at their records in the layer attribute table. The user can find features by using known information about the feature in order to search the map for that particular feature.

• Identifying Features:

Perhaps the fastest way to get information about a single feature is to identify it, using the Identify Tool.  

To use the Identify tool, the user must select it from the Tools Toolbar. Within the map, the user must click on the feature of interest in order to view the attribute information for that particular feature.

• Selecting Features:

If the user wants to compare information about several features, the best way is to select the features on the map and look at their records in the layer attribute table. The easiest way to select multiple features is by using the Select Features Tool on the Tools Toolbar.

To use the Select Features Tool, the user must select it from the Tools Toolbar. On the map, all features of interest may be selected by holding down the shift key and clicking on the various features of interest. The selected features will be outlined in blue. If a feature is selected by mistake it can be de-selected by holding down the shift key and clicking the feature again. All features that have been selected, can be cleared by clicking the Selection menu from the Standard Toolbar and selecting the Clear Selected Features option.

To view the selected features' attribute table, the user must right-click on the data layer where features have been selected. The Open Attribute Table option should then be clicked.

After the Open Attribute Table option has been selected, the attribute table will appear with all of the selected features highlighted in blue.

The user can group all of the selected attributes, by clicking on the Selected button at the bottom of the attribute table.  Only those features that were highlighted will appear.

Now the user can easily compare various attribute values, such as Area for each state. If the user wishes to see the states listed according to largest area, the user can right-click on the appropriate field name (in this case AREA), and the Sort Descending option may be selected from the context menu.

• Finding Features:

When the user has a piece of information about a feature, but is not sure where that feature is on the map, the user can search the map for that feature using the known piece of information.  

The user can find a feature, by selecting the Find tool on the Tools toolbar. When the Find dialog Box appears, the Features tab should be selected. The known attribute information should be typed in the Find box. In the In Layers drop down box, the layer that the user wishes to find features in should be selected. In the Search options, the user should choose to either search all fields in the attribute table or a specific field. Once all parameters are set, the Find button should be clicked.  

In the following example, the State of Arkansas was found in the U.S. State Data Layer by typing in the known attribute information (i.e. state name = Arkansas).

Once the Find button is clicked and the feature is found, the user can locate it on the map and get its attributes. This can be done when the user right clicks on the feature row found in the Find dialog box and clicks Identify Feature(s). The feature will briefly flash within the map display and the Identify Results dialog box will open.

In addition to identifying, selecting, and finding features, the user can select features by attributes by writing a query that automatically selects features that meet a specified criteria.  The simplest type of query consists of an attribute (such as STATE_NAME), a value (such as 'Arkansas'), and a relationship between the two (such as 'equal to'). A more complex query combines these simple queries using operators like 'and' / 'or'. These queries are constructed using Structured Query Language (SQL). ArcMap creates the query automatically in this format.  

To create an attribute query, the user must click the Selection menu on the Standard Toolbar. The Select by Attributes option should be clicked. In the Select by Attributes dialog box, the Layer drop down arrow should be clicked and the data layer of interest should be selected.

The fields in the attribute table appear in the Fields box on the left of the dialog box. When a particular field is highlighted, sample values display in the Unique values list on the right. If the user wishes to see all of the attribute values, the Complete List button may be selected. The buttons in the middle are used to choose operators and to connect queries.

To perform a query, the user must double-click an attribute field of interest, in order for it to display in the bottom portion of the Select by Attributes dialog box. Then the user must click on the appropriate operator button. A unique value of interest may be double clicked on within the Unique Values box, or a value may be directly typed into the query string.  

In the following example, all States were initially selected that had <= 300,000 households.

Then, all states were selected that had <= 300,000 Households AND <=300,000 Females.

Selecting Features by Location:

Instead of selecting features by their attribute values, the user may also select them by their location (their spatial relationship to other features, whether in another layer or in the same layer). To select features by location, the user specifies a selection method, a selection layer, a spatial relationship, a reference layer, and sometimes a distance buffer. 

To begin selecting features by location, the user must click the Selection menu and click the Select by Location option.  The Select by Location dialog box opens.

By default, the selection method is select features from.  This option should be used when the user wants to create a new selected set. The other options allow the user to add to an existing selected set of features, remove from an existing selected set of features, or select from an existing selected set of features.  

Within the scrolling list of selection layers, the user may select the layer from which they wish to select features.  

There is a list of spatial relationships that can be chosen using the drop down arrow. The following describes the various options that are available.

• Are Crossed by the Outline of: This method selects the features that are overlapped by the features of another layer.
• Intersect: This method selects any features that are overlapped by the features of another layer as well as those features that border the reference features.
• Are Within a Distance of: This method selects features near or adjacent to features in the same layer or in a different layer. The user must specify the numerical distance of interest.
• Have Their Center in: This method selects the polygon features in one layer that have their centroid in the polygon features of another layer.  
• Are Completely Within: This method selects features in one layer that fall completely inside the polygons of another.
• Completely Contain: This method selects polygons in one layer that completely contain the features in another layer.
• Share a Line Segment with: This method selects line and polygon features that share line segments with other features.  
• Touch the Boundary of: This method selects lines and polygons that share line segments, vertices, or end-points (nodes) with the lines in the layer. The lines or polygons will not be selected if they cross the lines in the layer.
• Are Identical to: This method selects any feature having the same geometry as a feature of another layer; however, the feature types (point, line, or polygon) must be the same.
• Contain: This method selects features in one layer that contain the features of another. The boundaries of the features ARE allowed to touch.
• Are Contained by: This method selects features in one layer that are contained by the features in another.

Next, the reference layer should be chosen using the drop-down arrow.

If the user wishes to apply a distance buffer, then the box next to the Apply a buffer to the features in ... option should be checked (or clicked). A distance and a unit of measure should be chosen.

Once all parameters are set, the Apply button should be clicked. The results will be selected in the map display.

In the following example, all major roads were selected that exist in Arkansas using a layer that contained only the Arkansas state polygon and a U.S. road layer that contained all major U.S. roads.

Once a feature has been selected in can be converted into its own ArcMap data layer. 

This can be done by right clicking on the name of the data layer in the table of contents that contains the selected feature of interest and clicking on the Create Layer from Selected Features option in the Selection menu.

The new layer will appear in the table of contents. This layer is given a default name that can be changed by right-clicking on the name, selecting properties, selecting the General tab, and typing in a new name in the Layer Name box.

End of Section 3.

Go to:
Section 1: Getting Started with ArcGIS: ArcCatalog, ArcMap, and ArcToolbox
Section 2: Manipulating Display in ArcMap
Section 3: Querying Data in ArcMap
Section 4: Preparing Data for Analysis in ArcMap
Section 5: Analyzing Data in ArcMap
Section 6: Making and Printing Maps in ArcMap
ArcGIS Introductory Tutorial front page.

Last modified: Tuesday, May 03, 2005