sqlANYindexcreate-index
sql
CREATE INDEX idx_orders_created_at ON orders (created_at);Useful for range scans, sorting, and recent-record lookups.
MySQL Indexes, EXPLAIN, and Performance Cheatsheet
index design, show index, explain, explain analyze, analyze table, and practical performance tuning workflows in MySQL.
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indexes
Create, inspect, and reason about indexes for common query patterns.
sqlANYindexcomposite-index
sql
CREATE INDEX idx_orders_user_status_created ON orders (user_id, status, created_at);Composite indexes can accelerate queries that filter by the leading columns.
sqlANYshow-indexmetadata
sql
SHOW INDEX FROM orders;Review cardinality, uniqueness, and column order when debugging plans.
sqlANYdrop-indexcleanup
sql
DROP INDEX idx_orders_created_at ON orders;Dropping unused indexes can reduce write amplification and storage cost.
explain and analysis
Understand how MySQL intends to execute a query and spot performance problems.
sqlANYexplainoptimizer
sql
EXPLAIN SELECT * FROM orders WHERE user_id = 42 ORDER BY created_at DESC LIMIT 20;`EXPLAIN` is the first stop when a query is unexpectedly slow.
sqlANYexplain-analyzeperformance
sql
EXPLAIN ANALYZE SELECT * FROM orders WHERE user_id = 42 ORDER BY created_at DESC LIMIT 20;Great for validating whether the expected index strategy is actually helping.
sqlANYanalyze-tablestatistics
sql
ANALYZE TABLE orders;Refreshing statistics can help the optimizer make better plan choices after large data changes.
sqlANYoptimize-tablemaintenance
sql
OPTIMIZE TABLE orders;Best used intentionally; its effect and cost depend on the storage engine and workload.
sqlANYexplainconnectiontroubleshooting
sql
EXPLAIN FOR CONNECTION 12345;Helpful during live troubleshooting when you have the blocking or long-running connection id.
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