Https://docs.microsoft.com/en-us/sql/relational-databases/tables/create-foreign-key-relationships
The answer is "smart guides".
Answer:
Create a validation rule using ISPICKVAL()
Explanation:
Solution
This can be achieved by creating a a validation rule using ISPICKVAL()
Create a Validation Rule Based on a Pick list
: The ISPICKVAL() are very important for creating validation rules that check whether a definite pick list value is chosen. for instance, say you want another person to enter a reason when they change a case's Status pick list value to increase.
