Answer
Index join keys, simplify join order, avoid functions on columns, and use covering indexes to reduce table lookups.
Quick Answer
Optimize multi-table JOIN performance: index every join column on the driving table's side (and ensure the joined table's PK or indexed FK). Reduce the result set before joining with WHERE on the earliest possible table. Use STRAIGHT_JOIN to force join order if the optimizer chooses wrong. Use EXPLAIN to verify join type is ref or eq_ref (not ALL). Minimize columns in SELECT to reduce memory usage.
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SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ