Go to Admin -> Stores -> Attribute -> Product -> Product Attributes.
Create Attribute as shown in Image.
Assign this Attribute to your Attribute Set. Create Product by selecting all Values. Test 1, Test 2, Test 3.
Update product by removing all values. It will not work. If you remove Test 2 & Tests 3. Then it will store Test 1.
It works fine for 1 Option. But if you want to remove all 3 of them, then it won't work.
Alternative would be to create "Select" as Option & assign
Values will be stored in
catalog_product_entity_varchar. Check ur
eav_attribute Table &
entity_id is Product Id