بهینهساز کوئری SQL
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Query optimization requires understanding execution plans. This prompt forces the AI to think about data volume and access patterns.
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Database optimization
پرامپت
Analyze the following SQL query for performance issues. Provide: 1) What makes it slow, 2) An optimized version with explanation, 3) Recommended indexes, 4) Estimated improvement. Consider table sizes of 1M+ rows.
نتیجه
**Problem**: The subquery in the WHERE clause executes for every row (correlated subquery).
**Optimized Query**: ```sql SELECT o.id, o.total, u.name FROM orders o JOIN users u ON o.user_id = u.id JOIN (SELECT user_id, MAX(created_at) as latest FROM orders GROUP BY user_id) latest_o ON o.user_id = latest_o.user_id AND o.created_at = latest_o.latest WHERE o.total > 100; ```
**Recommended Index**: `CREATE INDEX idx_orders_user_created ON orders(user_id, created_at DESC);`
Query optimization requires understanding execution plans. This prompt forces the AI to think about data volume and access patterns.
This prompt demonstrates a structured approach to database optimization, producing consistent, high-quality results that can be iterated upon.