Suppose i have a multi select picklist which has 30 items. Now i have to put a validation rule that "user can't choose all the items from picklist. Atleast one item should be available in available list."
How can i implement this validation.
I know i can do like " AND(INCLUDES(item_c,'1'),INCLUDES(item_c,'2'),INCLUDES(item__c,'3'),.... etc) for all values but i don't want to follow this approach as i will have to hard code all the values.