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SQL Worksheet
🗃 Indexes, Views & Performance
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After this worksheet you can
Speed lookups with indexesKnow index trade-offsCreate viewsRead EXPLAIN basics📚 Quick Recap
Indexes make queries fast; views make complex queries reusable. Together with EXPLAIN, they are the core tools of SQL performance tuning — helping you go from a 10-second query to a 10-millisecond one.
🧠 Section A · Concept Check ● BEGINNER 4 × 1 = 4
1An index speeds up:
2Indexes cost:
3A view is:
4See a query plan with:
🧮 Section B · Problem Solving ● INTERMEDIATE 2 + 3×3 = 11
5CREATE idx_email ON users(email);
6Primary keys are indexed .
7Index the orders.user_id column.
8Create a view of active users.
9When would you NOT add an index?
🚀 Section C · Challenge ● CHALLENGE 5
10What does EXPLAIN tell you?
💭 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-A 2-A 3-A 4-A | 5 INDEX 6 automatically 7 = CREATE INDEX idx_orders_user ON orders(user_id); 8 = CREATE VIEW active_users AS SELECT * FROM users WHERE active = 1; 9 = Small tables or write-heavy columns rarely searched | 10 = How the engine executes the query (index used, rows scanned)