Fragmentary knowledge points of MySQL

Write it at the front

This section is used to record MySQL Small pieces of knowledge in the learning process , It is also convenient for you to check later when sharing .

1： Slow log

The main parameters of the slow log are as follows ：

 Control switch ：slow_query_log
 Slow log writing execution time ：long_query_time
 Slow log files ：slow_query_log_file

The following settings ：

mysql> set global slow_query_log=1;
Query OK, 0 rows affected (0.04 sec)

mysql> show variables like 'slow_query_log';
+---------------------+---------------------------------------------------------------+
| Variable_name       | Value                                                         |
+---------------------+---------------------------------------------------------------+
| slow_query_log      | ON                                                            |
+---------------------+---------------------------------------------------------------+
1 rows in set (0.00 sec)

mysql> set long_query_time=0;
Query OK, 0 rows affected (0.00 sec)

mysql> show variables like 'long_query_time';
+-----------------+----------+
| Variable_name   | Value    |
+-----------------+----------+
| long_query_time | 0.000000 |
+-----------------+----------+
1 row in set (0.00 sec)

mysql> show variables like 'slow_query_log_file';
+---------------------+---------------------------------------------------------------+
| Variable_name       | Value                                                         |
+---------------------+---------------------------------------------------------------+
| slow_query_log_file | D:\program_files\phpstudy\PHPTutorial\MySQL\data\jhp-slow.log |
+---------------------+---------------------------------------------------------------+
1 row in set (0.00 sec)

In order to test the effect long_query_time Set to 0, So all the sql Statements are recorded in the slow log , For example, execute the following sql sentence ：

mysql> select count(*) from t;
+----------+
| count(*) |
+----------+
|   100000 |
+----------+

You can view the generated slow log ：

Written in the back

Refer to the list of articles ：

MySQL Slow query log （Slow Query Log） .