-- Suggested testing environment: -- http://sqlite.online/ -- Example case create statement: CREATE TABLE sessions ( id INTEGER NOT NULL PRIMARY KEY, userId INTEGER NOT NULL, duration DECIMAL NOT NULL ); INSERT INTO sessions(id, userId, duration) VALUES(1, 1, 10); INSERT INTO sessions(id, userId, duration) VALUES(2, 2, 18); INSERT INTO sessions(id, userId, duration) VALUES(3, 1, 14); -- Expected output: -- UserId AverageDuration -- ----------------------- -- 1 12