SQL Server 2019

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CREATE TABLE tablename (
  a VARCHAR(3),
  b VARCHAR(3),
  c INTEGER
);

INSERT INTO tablename
  (a, b, c)
VALUES
  ('AN8', 'USD', '99'),
  ('AN8', 'USD', null),
  ('AT0', 'EUR', null),
  ('AT0', 'EUR', null);
4 rows affected

select a, b
from tablename
group by a, b
having min(c) is null


a
b


AT0
EUR


Warning: Null value is eliminated by an aggregate or other SET operation.


select a, b
from tablename
group by a, b
having max(c) is null


a
b


AT0
EUR


Warning: Null value is eliminated by an aggregate or other SET operation.


select a, b
from tablename
group by a, b
having sum(c) is null


a
b


AT0
EUR


Warning: Null value is eliminated by an aggregate or other SET operation.


select a, b
from tablename
group by a, b
having avg(c) is null


a
b


AT0
EUR


Warning: Null value is eliminated by an aggregate or other SET operation.