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MySQL create events (CREATE EVENT)

In MySQL, an event is a task that runs based on a schedule. Therefore, it's also known as a scheduled event. Events are similar to cron jobs in UNIX or tasks in Task Scheduler in Windows.

The event scheduler is a MySQL feature that allows you to schedule tasks that run within the database environment. The tasks, also known as events, are executed according to a specific schedule.

Let's see how we can create an event in MySQL:

Enable Event Scheduler

First, make sure that event scheduler is enabled. You can check its status using the following command:

SHOW VARIABLES LIKE 'event_scheduler';

If the event scheduler is disabled, you can turn it on by running this command:

SET GLOBAL event_scheduler = ON;

Syntax to CREATE EVENT

Here is the basic syntax for creating an event:

CREATE EVENT event_name
ON SCHEDULE schedule
DO
event_body;

Where:

event_name: The name of the event.
schedule: Defines when and how often an event is executed.
event_body: The SQL statement to be executed.

The schedule can be a single occurrence or a recurring event. For example, AT timestamp [+ INTERVAL] or EVERY interval STARTS timestamp [+ INTERVAL] ENDS timestamp [+ INTERVAL].

Example

Let's consider an example where we create an event that deletes all rows from a log_table every day at 3 AM.

CREATE EVENT clear_log_table
ON SCHEDULE
  EVERY 1 DAY
  STARTS (TIMESTAMP(CURRENT_DATE) + INTERVAL 3 HOUR)
DO
  DELETE FROM log_table;

In this example, clear_log_table is an event that is scheduled to run every day (EVERY 1 DAY), starting at 3 AM (STARTS (TIMESTAMP(CURRENT_DATE) + INTERVAL 3 HOUR)). The action of this event is to delete all rows from log_table.

Note:

You must have the EVENT privilege for the database to create an event.
The event scheduler thread runs as the 'mysql' system user, so make sure this user has the necessary privileges to execute the event's SQL statement.
To see all events in the database, you can use the SHOW EVENTS statement.
To drop an event, use the DROP EVENT event_name statement.
To alter an event, use the ALTER EVENT event_name statement.

Creating scheduled events in MySQL:
- Scheduled events in MySQL allow you to automate tasks that occur at specified intervals.
```
-- Create a scheduled event in MySQL
CREATE EVENT event_name
ON SCHEDULE EVERY 1 DAY
DO
BEGIN
    -- Event logic
END;
```

How to use CREATE EVENT in MySQL:

Use the CREATE EVENT statement in MySQL to define and create a new scheduled event.

-- Create a scheduled event in MySQL
CREATE EVENT event_name
ON SCHEDULE EVERY 1 HOUR
DO
BEGIN
    -- Event logic
END;

MySQL event scheduling example:

Example of creating a scheduled event in MySQL that updates a timestamp every day.

-- Create a daily event to update timestamp
CREATE EVENT update_timestamp_event
ON SCHEDULE EVERY 1 DAY
DO
UPDATE my_table SET timestamp_column = NOW();

Defining events with MySQL:
- Define events in MySQL using the CREATE EVENT statement, specifying the event name, schedule, and the event logic.
```
-- Create a scheduled event in MySQL
CREATE EVENT event_name
ON SCHEDULE EVERY 1 WEEK
DO
BEGIN
    -- Event logic
END;
```

Creating and managing scheduled events in MySQL:

Create and manage scheduled events in MySQL by using the CREATE EVENT statement and altering or dropping existing events.

-- Create a scheduled event in MySQL
CREATE EVENT event_name
ON SCHEDULE EVERY 30 MINUTE
DO
BEGIN
    -- Event logic
END;

-- Alter a scheduled event in MySQL
ALTER EVENT event_name
ON SCHEDULE EVERY 1 HOUR;

Using parameters in MySQL events:

Use parameters in MySQL events to customize the behavior of the event logic.

-- Create an event with parameters in MySQL
CREATE EVENT event_name
ON SCHEDULE EVERY 2 DAYS
DO
BEGIN
    -- Event logic using parameters
END;

Executing and testing MySQL events:
- Execute and test MySQL events by observing their execution at scheduled intervals and verifying the expected results.
```
-- Manually execute the event
CALL event_name;
```