Basics of MySQL Query Optimization: Simple Query Speed-Up Tips for Beginners

This article explains the necessity and practical techniques of SQL query optimization, aiming to enhance system response speed and reduce user waiting time. Common mistakes for beginners include full table scans (without indexes), using SELECT * to return redundant fields, incorrect JOIN operation order, or improper use of functions. Core optimization techniques: 1. Add indexes to frequently queried fields (avoid duplicating primary key indexes and select fields with fewer duplicate values); 2. Clearly specify the required fields in SELECT to avoid redundant data; 3. Use the small table to drive the large table when performing JOINs; 4. Do not use functions on indexed fields (e.g., YEAR(create_time)); 5. Use EXPLAIN to analyze the query plan (focus on the 'type' and 'Extra' columns). Misconceptions to avoid: more indexes are not always better, OR conditions may cause index failure (replace with UNION ALL), and COUNT(DISTINCT) is inefficient. Optimization should first locate issues through EXPLAIN, prioritize mastering basic techniques, and avoid reinventing the wheel by leveraging case studies.