I created a Nintex form in SharePoint 2016. It is based on a List. I want to put a validation which prompts the user the the record already exists in the list.
For instance, when the user clicks on Save, the form should check 3 fields in the list. If the entry that user enters matches what is in the list, the user should get a warning and should not be able to save.
One alternative is to address this in your SP list. On the three columns that must contain unique values set the to "Enforce unique parameters:" parameter to "Yes". This will index the list for the three columns. Then if user attempts to save the form with a repeated value in one or more of the columns, a warning message will be returned on the top of the form.
@guru2000 try below approach: