B-Tree Indexes & EXPLAIN Query Analysis

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Accelerate lookups from seconds to milliseconds using B-Tree and composite indexes, and analyze bottlenecks with EXPLAIN.

How B-Tree Indexes Work

Without an index, MySQL must perform a full table scan, reading every row from disk. A B-Tree index maintains a self-balancing sorted search tree, allowing lookups in O(log N) operations.

Auditing Execution Plans with EXPLAIN

Try It Yourself »

-- Create a composite index
CREATE INDEX idx_user_status_created ON Orders (UserID, Status, CreatedAt);

-- Analyze execution plan
EXPLAIN SELECT * FROM Orders 
WHERE UserID = 450 AND Status = 'Shipped' 
ORDER BY CreatedAt DESC;

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Test Yourself With Exercise

+15 XP

Which SQL command analyzes the MySQL query planner execution strategy and reveals whether indexes are being utilized?

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