OBIEE11g: "NULL" Value in Prompts

In OBIEE 11g when we create a prompt on a column we can see "NULL" value is in the prompt. As it is the unwanted value we have to suppress this value. We can achieve this by following the below steps...

Step 1 : NULL is getting displayed in the Prompt

Step2 : Edit the prompt and look for the column on which the prompt is created

Step3 : Open the RPD in Online or Offline mode. Go to the physical layer and select the table, expand the table and select the column

Step 4 : Edit the properties of the column by double clicking on it.

Step 5 : Unchecked the Check box which says "Nullable".

Step 6 : Save the RPD and check the same on the dashboard. Now you can see the NULL value got disappeared.

NOTE : After saving the RPD changes it will take some time to reflect the result on the dashboard. Immediately you can not see the NULL value disappeared. It will take about an hour or so to reflect if you make the changes in Online Mode. If you restart the services then you can see the immediate expected result.
After making the changes in Online mode and saving it dont forget to clear the cache.