CREATE TABLE volume (Weeks_on_Top NUMBER, Artist_ID VARCHAR2)
CREATE TABLE artist (Artist_ID VARCHAR2, age VARCHAR2)

What is the average weeks on top of volumes associated with the artist aged 25 or younger?
SELECT AVG(T2.Weeks_on_Top) FROM artist AS T1 JOIN volume AS T2 ON T1.Artist_ID = T2.Artist_ID WHERE T1.age <= 25
SELECT AVG("T2"."Weeks_on_Top") FROM "artist" "T1" JOIN "volume" "T2" ON "T1"."Artist_ID" = "T2"."Artist_ID" WHERE "T1"."age" <= 25