task_4

SELECT c.* FROM SH.CUSTOMERS c
WHERE c.CUST_GENDER = 'M' AND c.CUST_INCOME_LEVEL LIKE 'D%' AND c.COUNTRY_ID IN ('US','DE')
-- попробовал двойное отрицание, работает
AND NOT EXISTS (
SELECT * FROM SH.CUSTOMERS s
WHERE c.CUST_MAIN_PHONE_NUMBER = s.CUST_MAIN_PHONE_NUMBER AND s.CUST_MARITAL_STATUS IS NOT NULL);