Check null for a column in all records in SQL

Hello

How to check for column all records are empty or null, is there any simple way to do it in SQL, like joins or grouping.

Name address phone

a addr1 phone1

b addr2 null

b addr3 null

c addr4 null

a addr5 phone2

If I want to check if all phone for b are null, what will be the easiest way.