Second Attempt Score Per User | Dataford Interview Questions

Khan Academy wants to analyze how students perform after their first attempt on a quiz exercise. Write a PostgreSQL query that returns the second attempt score for every student who attempted exercise 101 more than once.

Requirements

Rank attempts separately for each student and exercise by attempted_at ascending, using attempt_id as a tie-breaker.
Return only the second attempt for Khan Academy exercise 101.
Include students with a NULL second-attempt score, and sort the result by user_id.

Schema

users

Column	Type	Description
user_idPK	INT	Unique student identifier
username	VARCHAR(50)	Student username

exercises

Column	Type	Description
exercise_idPK	INT	Unique exercise identifier
exercise_name	VARCHAR(100)	Exercise title

quiz_attempts

Column	Type	Description
attempt_idPK	INT	Unique quiz attempt identifier
user_id	INT	Student who made the attempt
exercise_id	INT	Exercise attempted
score	NUMERIC(5,2)	Score from 0 to 100, possibly unavailable
attempted_at	TIMESTAMP	Timestamp when the attempt was submitted

Your question is Second Attempt Score Per User. Start with the requirements and the three tables in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem