I want the application to be notified when the database is changed.
I can't use trigger. Because we know the DB's connection message, but we can't modify the db.
So can anyway make application be notified by a connection, like oracle JDBC's Database Change Notification.
So can anyway make application be notified by a connection?
No.
There is a user-defined extension you could use, if you control your MySQL server, to send messages (amqp) from MySQL. You can use that extension in a trigger. https://github.com/mysqludf/lib_mysqludf_stomp#readme
Otherwise, you are out of luck on this. You need to add this notification functionality to the code you use to INSERT and UPDATE rows in your table.
Related
Some changes made in my database which is in server how to know who changes the data and what changes they made?
I'm not sure if it is possible in MySQL but in Oracle you can create system triggers to check who has logged in, which values have been changed etc.
I recommend you to surf in the MySQL triggers website and see if there's something that you need.
https://dev.mysql.com/doc/refman/8.0/en/triggers.html
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 have a BEFORE UPDATE trigger on one table. Now in that trigger, I want to identify whether the update query is sent from application (Java) or it is direct from database access, like a query from MySql command prompt.
Is it possible in MySql trigger ?
No. Triggers are fired independent of clients. They are not built for client specific concerns.
And hence you can't find which client's statement caused the trigger to fire.
At work we use amfphp as server and mysql as databse. What we need is that when a user updates a record the other users logged in the application can receive that update and see the update data, is that possible? Are there any libraries capable of doing this? I think that the most important part is to identify from the server the logged in users... thank you in advance.
To make this happen you will need to use a server that supports push functionality; meaning the server can send data to the client.
LiveCycle supports this, as does GraniteDS and WebOrb. I don't think that PHP does.
We need to deploy application(developed by Java) WAR file in client place which make use of MySql 5.0. But we would like to restrict the client (the application owner, not the webpage visitor) from modifying any data in the database. Is there any way to protect data. The client can make use of the application but they should not be able to change any value in database. How to do that?
Manage Role/User permissions
Create an sql user (you should already have one), which will have only SELECT permission. So it would be something like
GRANT SELECT ON db_base.* TO db_user#'localhost' IDENTIFIED BY 'db_passwd';
http://kb.mediatemple.net/questions/788/HOWTO:+GRANT+privileges+in+MySQL
http://blog.wl0.org/2010/01/managing-mysql-grants/
http://www.ntchosting.com/mysql/grant.html
Check links below for further reading
FOR MySQL
Best Practice for Designing User Roles and Permission System?
http://www.databasejournal.com/features/mysql/article.php/3311731/An-introduction-to-MySQL-permissions.htm
http://www.devshed.com/c/a/MySQL/MySQL-User-Account-Management/
Can't set permissions on MySQL user
http://www.aquafold.com/d7/docs/BD5C99E4-3B55-C812-8318-6338A9A89ED9.html
FOR SQL Server.
http://www.databasejournal.com/features/mysql/article.php/3311731/An-introduction-to-MySQL-permissions.htm
http://www.mssqlcity.com/Articles/Adm/SQL70Roles.htm
http://www.sql-server-performance.com/articles/dba/object_permission_scripts_p1.aspx
https://web.archive.org/web/1/http://articles.techrepublic%2ecom%2ecom/5100-10878_11-1061781.html
http://www.databasejournal.com/features/mssql/article.php/2246271/Managing-Users-Permissions-on-SQL-Server.htm
This is impossible; if you deploy the application at the client, he will have the credentials and will be able to log into the MySQL database and pretent he is the application. And thus he can make any change to the database that your application can.
The only way to solve this securely is to make a tier between the client and your MySQL database, and make sure that you control this so that it is only possible to make 'legal' changes.
Just write the code accordingly so that the user doesn't have any chance to modify the database? I.e. the code doesn't execute any INSERT or UPDATE and/or controls the access based on a login/role.
I honestly really don't forsee any problems here, or the code must be prone to SQL injection attacks.
Update: The above answer is actually irrelevant since the question is clarified. Turning into Community Wiki.