15个SQL优化技巧助你提升软件性能！

15个SQL优化技巧助你提升软件性能！

引用

CSDN

等

12

来源

1.

https://blog.csdn.net/2401_85742452/article/details/140338894

2.

https://blog.csdn.net/RetutghbxLouis/article/details/139673744

3.

https://blog.csdn.net/rachel_2016/article/details/139294620

4.

https://wenku.csdn.net/column/4yi1gfdyoa

5.

https://blog.csdn.net/m0_60511809/article/details/136286960

6.

https://cloud.baidu.com/article/3180168

7.

https://oceanbase.csdn.net/665d6ff1f146327b8ff9f7e8.html

8.

https://developer.aliyun.com/article/1514186

9.

https://www.cnblogs.com/huaweiyun/p/18208098

10.

https://juejin.cn/post/7390646355028541467

11.

https://www.cnblogs.com/yeyuzhuanjia/p/18607076

12.

https://learn.microsoft.com/zh-cn/troubleshoot/sql/database-engine/performance/troubleshoot-optimizer-timeout-performance

在软件开发中，SQL查询性能直接影响着应用的整体表现。一个低效的SQL查询可能会导致系统响应缓慢，用户体验下降。本文精选15个实用的SQL优化技巧，从查询优化、索引管理、表结构设计等多个维度，帮助开发者提升数据库性能。

1. 避免使用SELECT *

-- 不推荐
SELECT * FROM employees;

-- 推荐
SELECT first_name, last_name FROM employees;

2. 使用合适的JOIN类型

-- 不推荐
SELECT * FROM employees, departments WHERE employees.department_id = departments.id;

-- 推荐
SELECT employees.first_name, departments.department_name
FROM employees
INNER JOIN departments ON employees.department_id = departments.id;

3. 避免在WHERE子句中使用函数

-- 不推荐
SELECT * FROM employees WHERE YEAR(birthdate) = 1980;

-- 推荐
SELECT * FROM employees WHERE birthdate BETWEEN '1980-01-01' AND '1980-12-31';

4. 使用UNION ALL代替UNION

-- 不推荐
SELECT * FROM table1 UNION SELECT * FROM table2;

-- 推荐
SELECT * FROM table1 UNION ALL SELECT * FROM table2;

5. 避免使用OR条件

-- 不推荐
SELECT * FROM employees WHERE department_id = 1 OR department_id = 2;

-- 推荐
SELECT * FROM employees WHERE department_id IN (1, 2);

6. 为频繁查询的列创建索引

CREATE INDEX idx_age ON employees(age);

7. 使用覆盖索引

-- 不推荐
SELECT first_name, last_name FROM employees WHERE age > 30;

-- 推荐
CREATE INDEX idx_age_name ON employees(age, first_name, last_name);
SELECT first_name, last_name FROM employees WHERE age > 30;

8. 避免在索引列上使用函数

-- 不推荐
SELECT * FROM employees WHERE YEAR(birthdate) = 1980;

-- 推荐
SELECT * FROM employees WHERE birthdate BETWEEN '1980-01-01' AND '1980-12-31';

9. 定期维护索引

DBCC INDEXDEFRAG (employees, idx_age);
DBCC CLEANTABLE (employees);

10. 避免过度规范化

11. 使用合适的数据类型

12. 分区大表

13. 使用查询缓存

14. 避免深分页查询

-- 不推荐
SELECT * FROM employees ORDER BY id LIMIT 10000, 10;

-- 推荐
SELECT * FROM employees WHERE id > 10000 ORDER BY id LIMIT 10;

15. 监控和分析查询计划

EXPLAIN SELECT * FROM employees WHERE age > 30;

通过应用这些优化技巧，可以显著提升SQL查询性能，改善应用的整体表现。但需要注意的是，优化是一个持续的过程，需要根据具体场景和需求不断调整和改进。