What is MySQL event scheduler, and how do you create a scheduled event?

MySQL Event Scheduler is a built-in scheduling tool that enables the execution of events (i.e., SQL statements or a set of SQL statements) at specific times or on a periodic basis. This facilitates more automated database management, such as regularly cleaning logs, updating statistics, or backing up data.

To utilize MySQL Event Scheduler, first ensure the event scheduler is enabled. You can verify its status with the following command:

sql
SHOW VARIABLES LIKE 'event_scheduler';

If the event scheduler is not active, enable it using:

sql
SET GLOBAL event_scheduler = ON;

Creating a scheduled event is achieved via the CREATE EVENT statement. Below is an example that truncates a table named logs at midnight every day:

sql
CREATE EVENT IF NOT EXISTS clear_logs
ON SCHEDULE EVERY 1 DAY
STARTS (TIMESTAMP(CURRENT_DATE, '00:00:00') + INTERVAL 1 DAY)
DO
  TRUNCATE TABLE logs;

In this example:

• IF NOT EXISTS is optional and prevents errors when creating an event with the same name if it already exists.
• ON SCHEDULE defines the execution frequency; here, it is configured to run daily.
• STARTS specifies the initial execution time; here, it is set to begin at midnight of the current date.
• DO is followed by the SQL statement to execute, which in this case is truncating the logs table.

Additionally, you can modify existing events using ALTER EVENT or delete events with DROP EVENT. To view all current events, use:

sql
SHOW EVENTS;

By effectively leveraging MySQL Event Scheduler, you can significantly improve database management efficiency and performance.