I am testing my mysql database and currently using dbforge IDE. When I create an event, for accessing some values from a table, which is supposed to occur after sometime, but it's not running and I don't get an error either. Please let me know exactly how to schedule an event in dbforge properly. Thanks
By default event scheduler is disabled try check whether it is on or not.
show variables like 'event_scheduler';
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I see two events is running in mysql database. One is once in a day and another once in a hour. I need to get the source code of these two events. How can I get event source code? I need to alter that event. That's why I really need to get the existing event source.
Use the show create event command in mysql to retrieve the sql code run by the event.
I am developing a Delphi XE7 application with data stored in an online Mysql database. For the database access I use FireDAC. Because the application can be used on more than one computer simultaneously I need to be notified when a table is changed, so I can update the displayed information on each computer. FireDAC has a component called TFDEventAlerted which sounded like exactly what I need for this. But this component gives an error when activating (calling Register): [FireDAC][Phys][MySQL]-303. Capability is not supported.
I am not sure what this means, but after reading more about the component it seems Mysql does not support this type of events? If so: can anyone tell me whether there is another solution to accomplish the same?
Any help would be appreciated as I cannot seem to find a good solution.
Native MySQL doesn't have the push-notification feature you're hoping to use. To make this work you'll need to poll (to regularly run a query) to look for changes.
There are some ways to overcome this limitation if the scale of your system makes polling infeasible. You could add a user-defined function to your MySQL server, like this one to send messages: https://github.com/mysqludf/lib_mysqludf_stomp#readme
This won't work if you don't own the MySQL server; most hosting services won't allow you to install UDFs.
Or, you could build a message publish/subscribe app. This is pretty easy to do with the Amazon simple queuing service or with rabbitmq. But it's a different kind of system design from what you are probably used to.
In my article series about Firebird Database Events I proposed a solution based on message-oriented middleware. The middle tier of your application then would notify all interested parties about certain database events. Middle tier code would be database independent, all you need is a message broker who is specialized in reliable message delivery. An imaginary example for a 'after post' event handler is shown below:
procedure TAppDataModule.PurchaseOrderAfterPost(DataSet: TDataSet);
var
Notification: INotification;
begin
Notification := NotificationService.CreateNotification(PURCHASE_ORDER_TABLE_UPDATED);
Notification.SetIntProperty(PURCHASE_ORDER_ID, PurchaseOrderID.AsInteger);
NotificationService.Send(Notification);
end;
Popular free/libre open source message brokers are for example Apache ActiveMQ and RabbitMQ.
TFDEventAlerted control is not for MySQL database. That database doesn't support event model. If you want update data in "real time" then you must add manual request for changed data
Here are steps:
Add new field to your database table like "last_updated";
Fill that field by now() value on update or insert actions (by trigger or sql);
Add timer to delphi app and add request by SELECT MAX(last_updated) AS last_updated FROM my_table for last updated time;
If that time is new then request updated data by SELECT * FROM my_table WHERE last_updated >= :need_last_updated.
I'm currently writing my Main Assignment on my last semester at my study (IT-Engineering with Networking) and currently working with MySQL.
My question is: Is it possible to execute a Shell script/Command from within a MySQL Trigger/Procedure? Or can it be done from a CASE statement?
I've been searching around the internet and read that it's inadvisable to do it.
But I need a script to check a table in a database for alerts and then warn people if there is any.
If there is anyway else this could be done, then I'm open for ideas.
Any input will be appreciated :)
You can read this blog for triggering a shell script from MySQL:
https://patternbuffer.wordpress.com/2012/09/14/triggering-shell-script-from-mysql/. To summarize, two options are presented:
Polling. To improve performance, a trigger could record the change in another table which you poll instead.
MySQL UDF. Write your own plugin, and beware of security implications!
I think for your requirement just write a python/php/perl script which will connect your MySQL DB and query the alert table for any alert and accordingly show warning message on the screen or send email/sms warning.
Is there any event which detects changes in the database tables? Im trying to do a chat box. It works fine. Except that it needs to be refreshed at regular seconds of interval to get the data. But, this would eat up lot of server load. SO, i was thinking of a event which triggers any changes in the database data. Suggest me the best solution.
You could use triggers as presented in the comments. Problem with that: a trigger can only be triggered to execute an sql statemnt. So you could us a trigger, and create some kind of "activity" table with proper indexes. Problem: you still need to check this activity table! To reduce load, you should write a server component to your chat program that notifeis all clients. This way, only the server has to check to database regularly and not each client.
Without more information what language you are writing in, we can not help you more I guess.
Does anybody now how to find and view/browse the existing scheduler events in TOAD for MySQL, or how to find them with SQL as they are really metadata?
I always use SHOW EVENTS to see what the scheduler has up its sleeve for a given schema.
Example:
show events in my_schema;