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#0319
Products Never Sold
EasySQL15 min10 XP
Problem
Return product names that never appear in sales, ordered by product.
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
products(product_id INTEGER, product TEXT); sales(sale_id INTEGER, product_id INTEGER)
Examples
Example 1
InputBag has no sale row
OutputBag
The unmatched product has NULL sale_id after the LEFT JOIN.
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
InputBag has no sale row
Expected[["Bag"]]
The unmatched product has NULL sale_id after the LEFT JOIN.
Hidden Test Categories
Empty or missing matchesDuplicate rows or tiesNULL values where the pattern commonly breaks