Databases Reference
In-Depth Information
Exploring the event scheduler
The
Event
Scheduler
(
http://dev.mysql.com/doc/refman/5.1/en/events.
html
), another new feature of MySQL 5.1, permits the creation of tasks that will run
automatically according to a schedule. The schedule is quite flexible and permits, for
example, a statement to be run every ten seconds, starting from midnight of May 18,
2011. These can be one-time events or recurring ones.
Activating the scheduler
We should first verify whether the scheduler is active on our server. If not, we need
to activate it. Otherwise, nothing will happen! We will start by entering the following
statement in the query box:
SHOW VARIABLES LIKE 'event%';
Next, we look in the results for a variable named
event_scheduler
. If this variable
is set to
OFF
, we need to ask the system administrator (or someone with the
SUPER
privilege) to execute the following statement:
SET GLOBAL event_scheduler = ON;
Granting EVENT permission
Every user who wants to create or drop an event needs the
EVENT
privilege, either
globally or on the database on which he or she plans to add the event. Please refer to
Chapter 19
for details about granting such privileges.
Creating an event
The current phpMyAdmin version does not have an interface on which we could
choose the various parts of the
CREATE EVENT
statement. Therefore, the only method
left is to use the SQL query box to enter the statement and to understand its syntax!
Here, we will use a totally fictitious example:
CREATE EVENT add_page_count
ON SCHEDULE
EVERY 1 MINUTE
DO
UPDATE author set total_page_count = total_page_count + 1
WHERE id = 1;
You can now get some amusement by browsing the
author
table once in a while,
and see the counter incrementing for author 1.
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