mysql语句执行时间查看

爱被打了一巴掌 2022-08-25 10:58 31阅读 0赞

打开语句分析并确认是否已经打开

mysql> set profiling=1;     
       Query OK, 0 rows affected (0.00 sec)  
        
       mysql> select @@profiling;  
       +-------------+  
       | @@profiling |  
       +-------------+  
       |           1 |  
       +-------------+  
       1 row in set (0.01 sec)

1.清除缓存

reset query cache ;

flush tables;

2.查看表的索引：

show index from tablename;

查看其执行计划：

我们可以很清晰的看到走的是全表扫描，而没有走索引！

查询消耗的时间：

mysql> show profiles;  
       +----------+------------+-----------------------------------------------------------------------------------------------------------------------------------+  
       | Query_ID | Duration   | Query                                                                                                                             |  
       |       54 | 0.00177300 | select * from person4all                                                                                                          |  
       |       55 | 0.00069200 | explain select * from person4all                                                                                                  |  
       +----------+------------+-----------------------------------------------------------------------------------------------------------------------------------+

全表扫描总共话了0.0017730秒