52 SQL Statement Performance Optimization Strategies

This article presents a comprehensive collection of 52 practical strategies for optimizing SQL query performance.

Key recommendations include creating appropriate indexes on WHERE and ORDER BY columns, avoiding full table scans, minimizing use of NULL checks, avoiding NOT EQUAL operators, replacing OR conditions with UNION ALL, preferring IN/EXISTS appropriately, using BETWEEN instead of IN for ranges, and avoiding functions or expressions on indexed columns.

It advises limiting the number of indexes per table (preferably no more than six), using numeric data types, preferring VARCHAR over CHAR, selecting specific columns instead of '*', employing table aliases, leveraging temporary tables or table variables wisely, and using NOLOCK only under safe conditions.

Additional tips cover query rewriting (e.g., using LIKE 'prefix%' instead of '%suffix'), batch inserts/updates, avoiding unnecessary GROUP BY, using EXPLAIN to analyze execution plans, choosing suitable storage engines (MyISAM vs InnoDB), optimizing data types (e.g., using MEDIUMINT, TIMESTAMP), and regular index maintenance.

Examples of improved queries are shown, such as SELECT * FROM record WHERE card_no LIKE '5378%' and SELECT * FROM record WHERE amount < 1000*30 , demonstrating dramatic reductions in execution time.