SQL Server 2019

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select *
into callrecord
from (values ('1',null)
     , ('2',5 )
     , ('3',null )
     , ('4',1 )
     , ('5',null ) ) z(callid,rating); 
5 rows affected

select * from callrecord;

callid
rating

1
null

2
5

3
null

4
1

5
null

select count(*) as total from callrecord;
select count(*) as rated, avg(rating) as average_rating from callrecord where rating is not null;
select count(*) as unrated from callrecord where rating is null;

total

5

rated
average_rating

2
3

unrated

3

callid	rating
1	null
2	5
3	null
4	1
5	null