Why OR Queries Break MySQL Indexes and How to Fix Them

This article explains how MySQL OR conditions can cause index loss, demonstrates typical scenarios with multi‑field, range, and dynamic filters, and provides practical solutions such as using UNION/UNION ALL or adding appropriate indexes to restore efficient query performance.

Index OptimizationOR querySQL

0 likes · 7 min read

Why OR Queries Break MySQL Indexes and How to Fix Them

Senior Brother's Insights

Oct 7, 2025 · Databases

Why MySQL OR Queries Often Skip Indexes—and How to Fix Them

This article explains how MySQL's OR conditions can cause index loss, provides concrete query examples, analyzes why the optimizer falls back to full table scans, and offers practical solutions such as rewriting with UNION or adding missing indexes to restore efficient index usage.

Index OptimizationOR querySQL

0 likes · 7 min read

Why MySQL OR Queries Often Skip Indexes—and How to Fix Them