ArcGIS Online

Overview of Joins

What is an Attribute Join?

An attribute join is used to append the fields of one table to another based on a common field. In order for an attribute join to work, the common field needs to be the same field type (e.g., string, numeric, etc.) and have identical formatting. The column names do not need to match in order for the attribute join to work.

For example, an attribute join could be used on the following fields (GEOID10 and ct10_id) to help append American Community Survey data to a shapefile showing Middlesex County, MA census tracts. The column names don't match, but the fields have identical formatting and the same field type (text). Once the attribute join is complete, the variables from the appended American Community Survey table can be visualized on the map by census tract.
          

Get Started with Attribute Joins

Create an Attribute Join

1. In Map Viewer, go to the left-hand menu and click Add. Browse to your file and add the spatial layer that you want to use for your attribute join (e.g., Middlesex County, MA Census Tracts).
2. In the right-hand menu bar, select Analysis. If the menu bar is grayed out, make sure you've added / selected the target layer for your join.
   
    
3. Go to Tools > Summarize Data > Join Features.
   
    
4. In the Join Features tool menu, select your Input features for your attribute join. The Target layer will be the feature layer that you want to add additional data to (e.g., administrative boundaries). The Join layer will be the data that you want to append to the target layer (e.g., spreadsheet data).
   
    
5. Under Join settings, select the attribute table columns from the target layer and join layer that you want to use for your attribute join. These columns must have the same field type (e.g., string, numeric) and formatting for the join to work. The column names do not need to match.
   
   
    
6. Select your Join operation and settings (e.g., join one to one, only keep first matching record).
   
    
7. Confirm your Join Type. The Inner Join / Left Join settings work like the Keep Matching Records / Keep All Records feature in the desktop software.
   
    
8. Enter an output name for your file. Try to avoid using spaces in your filename.
   
    
9. Confirm that your Environment Settings are correct. Make sure that your processing extent is set to the correct settings. If it isn't your analysis may only run on a subset of your data set.
   
    
10. Estimate your credit usage, then click Run.
    

What is a Spatial Join?

A spatial join uses geographic proximity to combine two or more spatial features on a map. A spatial join can visualize target features that intersect, completely contain, fall within a specified distance, etc. of the join features. 

Create a Spatial Join

The process for creating a spatial join in ArcGIS Online is similar to creating an attribute join.

1. Add your first spatial layer to Map Viewer, then go to the Analysis menu > Summarize Data > Join Features.
2. Add your target and join layers as input features. Both of these layers need to be spatial (i.e., not a spreadsheet) in order for the spatial join to work.
3. Under Join Settings, select Use spatial relationship, then select a spatial relationship from the drop-down menu. The available options will depend on the geometry type of your target and join layers (e.g., point, lines, polygons). 
   
    
4. Select your join type (inner join or left join). 
5. Enter an output name for your result layer file. Try to avoid using spaces in your filename.
6. Confirm that your Environment Settings are correct. Make sure that your processing extent is set to the correct settings. If it isn't your analysis may only run on a subset of your data set.
7. Estimate your credit usage, then click Run.

Note: If your spatial join doesn't produce your intended results, check that you have your target and join layers in the correct order and that you selected the correct spatial relationship parameters.