How to Optimize MySQL Queries: Practical Techniques

Slow queries waste everyone's time — yours, your dashboard's, and your server's. Most optimisation wins come from a short list of repeatable techniques rather than dark magic.

Key Points

• Index the columns in your WHERE, JOIN and ORDER BY clauses
• Select only needed columns — SELECT * drags extra data through the network
• Never wrap indexed columns in functions: WHERE YEAR(dt)=2026 kills the index; use ranges instead
• Use LIMIT when exploring large tables
• Prefer EXISTS over IN for large subquery results
• Read EXPLAIN before and after each change to confirm the improvement