How to know that the SQL statements executed in the database are slow

The website access speed is too slow. We need to check all links that may drag down the website speed, here we will share some of the SQL statements in the database that have been executed with low efficiency to help us better optimize our website programs.

(1) set it in the MySQL configuration file. The specific location is my. ini/my. cnf. Enable MySQL slow query output: log_slow_queries and set its value to ON.

(2) set it on the MySQL client. Connect to the MySQL database server through a client and run the following SQL statement:

Set global log_slow_queries = ON; set global long_query_time = 3;

Here, you can record the SQL statements that take more than or equal to 3 seconds and output them to the log file. You may not know where this log file is stored? Run the following command on the MySQL client:

Show variables like 'slow _ query_log_file ';

The location of the log query file is displayed.

For the above two methods, I personally recommend the second one, because this method does not need to restart the MySQL service. Remember that the first method needs to restart the MySQL service!

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