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My Solution to this Challenge
After the last challenge I was curious about being more efficient with sub-queries. This was the final code I got that avoided hard coding the room id:
SELECT NAME FROM SUBJECTS WHERE ID IN (SELECT SUBJECT_ID FROM CLASSES WHERE ROOM_ID = (SELECT ID FROM ROOMS ORDER BY CAPACITY DESC LIMIT 1));
I noticed I didn't need to add a Distinct keyword to exclude the duplicates with this answer. I'm assuming this is because my WHERE statement is technically pulling from a table that only populates each class id once?
Steven Parker217,639 Points
The second WHERE actually does return duplicate IDs, but the first WHERE is using the "IN" operator so it doesn't matter how many times a value appears in a result set, only if it exists in it or not.