Answer
The optimizer evaluates table statistics, cardinality, join orders, and cost estimates. It chooses the lowest I/O and CPU cost plan, relying heavily on accurate table statistics.
Quick Answer
MySQL query optimizer builds an execution plan by: parsing the query, transforming it (subquery flattening, constant folding), generating candidate plans (different join orders, index choices), estimating costs using table statistics (row counts, cardinality, index size), and picking the lowest-cost plan. Run EXPLAIN FORMAT=JSON to see detailed cost estimates. ANALYZE TABLE updates the statistics the optimizer uses.
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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