Validating Non Mandatory column

Hi,

Generally, if it is not mandatory column we can validate the same through out of the box.

But through one of my colleague I got to know the way by writing the formula i.e.

Navigate to the list->List Settings->Click on the column name ‘dept’

There under column name, formula has been applied as below

Now without selecting any value in the dept column when we try to save the value we shall be getting the validation message as below

This works out only when we try to add the new item in the list.

But when we try to edit the existing values this would not be applicable.