How to find distinct columns in a nested subquery in SQL?

Question

I need to find the distinct drinkers that ordered \'VODKA\' and \'WHISKY\'. I AM ONLY ALLOWED TO USE A NESTED QUERY. No other format is accepted.

I am quite new to sql

Answer 1

You could use an hanving for count distinct drink group by DRINKER

SELECT DRINKERS.DRINKER
FROM DRINKERS
INNER JOIN ORDERS DRINKERS.DRINKER = ORDERS.DRINKER
WHERE ORDERS.DRINK IN ( 'VODKA' , 'WHISKY')
GROUP BY DRINKER
HAVING COUNT(DISTINCT ORDERS.DRINK ) = 2 

or if you need a nested

    SELECT DISTINCT DRINKER
    FROM DRINKERS
    WHERE EXISTS (SELECT DRINKER 
                  FROM ORDERS
                  WHERE DRINK IN ( 'VODKA' AND 'WHISKY')
                  GROUP BY DRINKER
                  HAVING COUNT(DISTINCT ORDERS.DRINK ) = 2 
                  );