/*Writing an aggregated column
Assuming the column/field name is 'col'*/
SUM(CASE WHEN col IS NULL THEN 1 ELSE 0 END) count_nulls
/*OR*/
COUNT(*)-COUNT(col) count_nulls
SELECT COUNT(1) FROM my_table WHERE my_column IS NULL;
select sum(case when a is null then 1 else 0 end) count_nulls
, count(a) count_not_nulls
from us;
SELECT COUNT(*)
FROM Employee
WHERE email IS NULL;