如何定位并優(yōu)化慢查詢sql

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• 根據(jù)慢日志定位慢查詢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                                       |    查詢時間
  | 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                                             | .  慢日志是否打開
  | 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;   開啟慢查詢?nèi)罩荆ㄗ詈脤懺谂渲梦募?
  mysql> set global long_query_time = 1;   設置慢日志查詢時間
  
  
  mysql> show status like "%slow_queries%";
  +---------------+-------+
  | Variable_name | Value |
  +---------------+-------+
  | Slow_queries  | 0     |    慢查詢出現(xiàn)的次數(shù)
  +---------------+-------+

• 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，相信大家對“如何定位并優(yōu)化慢查詢sql”有了更深的了解，不妨來實際操作一番吧！這里是億速云網(wǎng)站，更多相關內(nèi)容可以進入相關頻道進行查詢，關注我們，繼續(xù)學習！