Activity Participants
A medium-tier problem at 72% community acceptance, tagged with Database. Reported in interviews at IBM and 0 others.
Activity Participants is a medium-difficulty database problem that shows up in SQL assessments at IBM and similar enterprises. If you're prepping for an OA, this one tests whether you can wrangle participant data without overthinking it. The 72% acceptance rate means it's not a trick question, but it's also not free. Most candidates who fail it make the same mistake: they assume they need complex joins or window functions when the real pattern is simpler. If you hit this live and your instinct misfires, StealthCoder will surface the working solution in seconds, invisible to the proctor.
Companies that ask "Activity Participants"
Activity Participants is the kind of problem that decides whether you pass. StealthCoder reads the problem on screen and surfaces a working solution in under 2 seconds. Invisible to screen share. The proctor sees nothing. Made by a working FAANG engineer who treats the OA the way companies treat hiring: as a game with rules you should know.
Get StealthCoderActivity Participants typically asks you to identify participants, count their activity, or filter by some participation criterion. The gotcha is usually one of these: joining multiple tables without accidentally creating duplicates, handling null participants correctly, or distinguishing between 'participated at least once' vs. 'participated in all activities.' The obvious approach often fails because candidates over-aggregate or miss an edge case in the join logic. Most solutions live in GROUP BY plus a HAVING clause, but the specific condition trips people up. When you're under pressure in the assessment and you're not 100% sure which direction to go, StealthCoder reads the schema and problem statement, then delivers a tested query that passes all test cases before you second-guess yourself.
Pattern tags
You know the problem.
Make sure you actually pass it.
Activity Participants recycles across companies for a reason. It's medium-tier, and most candidates blank under the timer. StealthCoder is the hedge: an AI overlay invisible during screen share. It reads the problem and surfaces a working solution in under 2 seconds. Made by a working FAANG engineer who treats the OA the way companies treat hiring: as a game with rules you should know. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Activity Participants interview FAQ
Is Activity Participants actually asked in live interviews?+
Yes. IBM's hiring pipeline includes it, and similar enterprises use it for database roles. The 72% pass rate suggests it's a screening filter, not a gimmick. It's not as trendy as some graph or dynamic programming problems, but it's stable, which means your prep now translates directly to future OAs.
What's the main trick to Activity Participants?+
Getting the join cardinality right. Most people write a query that works on the happy path but explodes when a participant appears in multiple activity records. The fix is often a DISTINCT in your SELECT or a GROUP BY that isolates participant identity before you count. Test your logic on edge cases first.
Do I need window functions for this problem?+
Probably not. Window functions are overkill here. Stick to GROUP BY, HAVING, and standard joins. If you're reaching for RANK() or ROW_NUMBER(), you've overcomplicated it. Simpler queries are faster to write, less error-prone, and easier to debug under time pressure.
How does Activity Participants compare to other database problems?+
It's solidly mid-tier. Not as basic as counting rows, not as hairy as recursive CTEs or complex aggregations. It rewards clarity of thought about join behavior and aggregation scope. Good prep for enterprise database roles where you need to ship correct SQL fast.
Should I memorize the exact solution?+
No. Understand the schema and the aggregation pattern instead. Every version of this problem has different tables and different business logic. Learn to spot when you need DISTINCT, when GROUP BY is the right lever, and how to test for duplicate rows before committing your answer.
Want the actual problem statement? View "Activity Participants" on LeetCode →