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FAQ: Why are incorrect results returned when filtering empty strings using the 'is blank' and 'is not blank' filter expressions in Web AppBuilder for ArcGIS?

Question

Why are incorrect results returned when filtering empty strings using the 'is blank' and 'is not blank' filter expressions in Web AppBuilder for ArcGIS?

Answer

Incorrect results are returned when filtering empty strings using the is blank and is not blank filter expressions in Web AppBuilder for ArcGIS because the filter setting is not properly configured.

The example uses a list of 28 attractions in New York City; 22 of which have the Review column filled while six others remain blank. However, the image below shows only four features are returned when the Review is blank expression is used.

Results of the wrong filter setting.

The following are best practices to ensure correct results are returned when filtering empty strings using the is blank and is not blank filter expressions in Web AppBuilder for ArcGIS:

Enable one filter at a time
In Web AppBuilder for ArcGIS, filtering can be applied from the attribute table using the Filter widget. Enable either one of the filters at a time to return the correct result.

Only use one filter at a time.

Uncheck the 'Enable Filter by map extent by default' option
When configuring the Attribute Table widget, uncheck the Enable Filter by map extent by default option in the Configure Attribute Table dialog box.

Uncheck the Filter by map extent option.
 
Note:
As an alternative, open the attribute table and click the blue-colored Filter by map extent icon This is the Filter by map extent icon. to disable the function. Clicking this icon turns the color of the icon to black. This indicates the filter is working on the total data instead of at a certain extent.

Enable the Filter result from the slider
By default, the Filter result is not shown automatically on the map. To view the Filter result, click the Filter widget and slide the Filter slider This is the Filter slider. to the right.

This is the Filter slider.

Use the 'is blank' or 'is not blank' selection from the drop-down list
In the Configure Filter dialog box, filter the blank value by selecting the is blank or is not blank option from the second field (operator) drop-down list, instead of selecting is or is not in the second field (operator) and typing blank in the third field (value/field/unique).

Select the 'is blank' and 'is not blank' options.

Configuring the Filter settings properly returns the correct results, as described below:
  • Configuring the Review is blank expression returns six features, as expected.

    Using the 'is blank' expression.
     
  • Configuring the Review is not blank expression returns 22 features, as expected.

    Configuring the 'is not blank' expression.

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