本篇内容主要讲解“如何定位并优化慢查询sql”，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习“如何定位并优化慢查询sql”吧!
根据慢日志定位慢查询sql
mysql> show variables like "%query%";
+------------------------------+-------------------------------------------------+
| Variable_name | Value |
+------------------------------+-------------------------------------------------+
| binlog_rows_query_log_events | OFF |
| ft_query_expansion_limit | 20 |
| have_query_cache | YES |
| long_query_time | 10.000000 | 查询时间
| query_alloc_block_size | 8192 |
| query_cache_limit | 1048576 |
| query_cache_min_res_unit | 4096 |
| query_cache_size | 1048576 |
| query_cache_type | OFF |
| query_cache_wlock_invalidate | OFF |
| query_prealloc_size | 8192 |
| slow_query_log | OFF | . 慢日志是否打开
| slow_query_log_file | /usr/local/mysql/data/tandeMacBook-Pro-slow.log | 慢日志log位置
+------------------------------+-------------------------------------------------+
mysql> set global show_query_log = on; 开启慢查询日志（最好写在配置文件）
mysql> set global long_query_time = 1; 设置慢日志查询时间
mysql> show status like "%slow_queries%";
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Slow_queries | 0 | 慢查询出现的次数
+---------------+-------+
使用explain等工具分析sql
mysql> explain select * from t_employee where name = "汪燕";
+----+-------------+------------+------------+------+-------------------+-------------------+---------+-------+------+----------+-------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+------------+------------+------+-------------------+-------------------+---------+-------+------+----------+-------+
| 1 | SIMPLE | t_employee | NULL | ref | idx_employee_name | idx_employee_name | 50 | const | 1 | 100.00 | NULL |
+----+-------------+------------+------------+------+-------------------+-------------------+---------+-------+------+----------+-------+
到此，相信大家对“如何定位并优化慢查询sql”有了更深的了解，不妨来实际操作一番吧！这里是天达云网站，更多相关内容可以进入相关频道进行查询，关注我们，继续学习！