BitWithBite
SQL Worksheet
🗃 Subqueries
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Nest a query inside anotherUse subqueries with INCompare against aggregatesKnow when a JOIN is better📚 Quick Recap
A subquery is a SELECT statement nested inside another SQL statement. They can appear in the WHERE clause, FROM clause, or even the SELECT list — letting you answer complex questions in a single query without temporary tables.
🧠 Section A · Concept Check ● BEGINNER 4 × 1 = 4
1A query inside a query is a:
2price > (SELECT AVG(price)...) compares to:
3id IN (SELECT user_id FROM orders) finds users:
4Subqueries go inside:
🧮 Section B · Problem Solving ● INTERMEDIATE 2 + 3×3 = 11
5Subqueries are wrapped in .
6WHERE id (SELECT ...) tests list membership.
7Products more expensive than average.
8Students in the class with the top average.
9Users who placed at least one order (subquery).
🚀 Section C · Challenge ● CHALLENGE 5
10When prefer a JOIN over a subquery?
💭 Reflection — the most useful thing I learned:
A ___/4 B ___/11 C ___/5 Total ___/20
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✂ answer key — fold or cut before handing out
1-B 2-B 3-B 4-A | 5 parentheses () 6 IN 7 = SELECT * FROM products WHERE price > (SELECT AVG(price) FROM products); 8 = WHERE class_id = (SELECT class_id ... ORDER BY AVG DESC LIMIT 1) 9 = WHERE id IN (SELECT user_id FROM orders) | 10 = When you need columns from both tables or better performance