Answer
An execution plan describes how MySQL executes a query. Using EXPLAIN reveals join types, index usage, and potential performance problems.
Quick Answer
EXPLAIN shows the query execution plan without running the query. Key columns: type (ALL=full scan, index, range, ref, const - const is best), key (index used), rows (estimated rows examined), Extra (Using where, Using index, Using filesort, Using temporary). Using filesort and Using temporary signal potential performance issues. Always run EXPLAIN on slow queries before adding indexes.
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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