find the names of all patients who have an undergoing treatment and are staying in room 111
SELECT DISTINCT T2.name FROM undergoes AS T1 JOIN patient AS T2 ON T1.patient  =  T2.SSN JOIN stay AS T3 ON T1.Stay   =   T3.StayID WHERE T3.room   =   111
patients who have an undergoing treatment refers to JOIN between undergoes and patient tables; staying in room 111 refers to stay.room = 111; names of all patients refers to SELECT DISTINCT name;