data analyst intern sql round, bangalore, 45 min

no leetcode thankfully. orders table + users table. they asked weekly active users, repeat purchase rate, and why left join changes the count. then one of them said this query is slow, talk. they didn't want a perfect index answer, just that i'd look at explain and not guess. i wasted time grinding pandas. they didn't ask pandas once. group by + window functions the week before was enough. that's the whole round.