WITH null_check1 AS
(SELECT cases + new_cases_per_million + deaths + icu_patients +
        hosp_patients + tests + reproduction_rate +
        new_vaccinations + stringency_index AS plus_col
   FROM covid19_data
),
null_check2 AS
(SELECT CASE WHEN plus_col IS NULL THEN 'NULL'
             ELSE 'NOT NULL'
        END chk
   FROM null_check1
)
SELECT chk, COUNT(*)
  FROM null_check2
 GROUP BY chk;