Come trovare colonne distinte in una sottoquery nidificata in SQL?

Potresti usare un gruppo di bevande distinto per il conteggio di 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 

o se hai bisogno di un

    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 
                  );