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#0325
Distinct Products Per User
EasySQL15 min10 XP
Problem
Return user_id and distinct_products purchased by each user.
Why This Matters
SQL interviews usually test whether you can turn a business question into the right rows, grouping level, join type, and edge-case behavior.
Schema
orders(user_id INTEGER, product TEXT)
Examples
Example 1
Inputuser 1 bought Book twice and Pen once
Outputuser 1 -> 2
COUNT(DISTINCT product) counts Book once for user 1.
Constraints
- Return only the requested columns.
- Use deterministic ORDER BY when multiple rows are returned.
- Assume SQLite-compatible SQL unless the prompt states otherwise.
CodeSQL
Visible browser tests run here when available.
Testcases1 visible / 3 hidden categories
Core SQL case
Inputuser 1 bought Book twice and Pen once
Expected[[1,2],[2,1]]
COUNT(DISTINCT product) counts Book once for user 1.
Hidden Test Categories
Empty or missing matchesDuplicate rows or tiesNULL values where the pattern commonly breaks