Practice — CodeArena

Status	Title	Technology	Topic	Acceptance	Difficulty
○	15.Find duplicate invoices	SQL	Deduplication	12.5%	Easy
○	2.Rolling 7-day active users	SQL	Window functions	—	Medium
○	5.Top N products per category	SQL	Aggregation	—	Easy
○	8.Sessionize clickstream events	SQL	Window functions	—	Hard
○	13.Second highest salary per department	SQL	Window functions	100.0%	Easy
○	14.Month-over-month revenue growth	SQL	Window functions	—	Medium
○	16.Running balance per account	SQL	Window functions	—	Medium
○	18.Gaps and islands in device uptime	SQL	Window functions	—	Hard
○	19.Cohort retention by signup month	SQL	Data modeling	—	Hard
○	20.Latest price as of each order	SQL	Data modeling	—	Medium