I have inherited support for an application used by a number of charities.
The application uses an Access database for local storage and has a web based interface with a MySQL database.
The application syncs data to the MySQL database using a Devart MySQL connector but this is constantly giving the following error:
Concurrency violation: the Update Command affected 0 of the expected 1 records.
I've checked and I think this is due to a setting in Devart Found records but as I can't recompile the application I don't think there's a way to fix it from that side.
Are there any changes I can make from the database side to prevent these errors?
Setting "FoundRows=true;" in the connection string is the only way to change the provider behavior. Please check your application, maybe it allows modifying the connection string via its *.config file?
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The access database is on server in folder. I need to create a stored procedure to connect to the access database and update the table data. It can be truncate then an insert. It is connecting via stored procedure to the access database i cannot figure out. It has to be done via a job on a schedule.
MySQL (the Sun- then Oracle- owned product) lacks the plumbing to connect to external tables unless they're on other MySQL servers. That is, it only has a FEDERATED storage engine. So, with MySQL you'll have to find some other way to handle your requirement; a MySQL event or other stored code cannot hit your Access tables.
MariaDB, the MySQL fork, has a CONNECT storage engine. It allows the server to hit external tables via ODBC, so you can hit Access with it. MariaDB is almost entirely compatible with MySQL, so maybe you can replace your MySQL server with it. The CONNECT documentation says this, however.
...these table types cannot be ranked as stable. Use them with care in production applications.
To me, that warning means don't do it!. Especially with a busy business-critical application (like a credit department might use) you don't want even a little bit of instability. If you truncate a table and then the reload fails, you'll be able to hear users yelling from the next county.
Your requirement is, I believe, to extract the contents of one (or more) Access tables and import them into a MySQL table. That kind of operation is called extract-transform-load etl. It seems you use SSIS for the purpose. That should work, because SSIS can connect to Access (of course) and to MySQL via the Connector/net or Connector/ODBC drivers.
But, scheduled SSIS packages get run from SQL Server database servers. You didn't say you have one of those at your disposal. If your org does have a production SQL Server instance, you can put your Access - to - MySQL package into it.
Otherwise you will have to figure out a way to run your scheduled etl job without relying on a database job (or event, as they're called in the MySQL world). For that you'll use the Task Scheduler on Windows, or a cronjob on a UNIX-derived OS like Linux or FreeBSD.
I bet you can do this work reliably from a Windows PowerShell script or a Linux shell script.
I was wondering if it is possible to create custom MySQL servers in VB.NET while working in visual studio at runtime so that if the server already exists it connects and if it isn't there, the code creates the server. I have searched for this everywhere but couldn't find anything. I would appreciate it a lot if someone guides me to the right path.
You could certainly write some .net code to start a MySQL server on your Windows box when an attempt to connect fails. You simply get a cmd.exe console with administrator privileges and give the command net start mysql.
But MySQL must already be installed on the box for that to work.
You might investigate Sqlite. It provides SQL locally to a .net program, storing your tables in a file called whatever.db. It has very similar .net API access to MySQL's Connector/Net and SQL Server's connector. It's in a NuGet package.
I don't completely understand your "custom MySQL servers" requirement. Sqlite gives you a way to use SQL in your application without connecting to a shared server. That may do what you need.
MySQL does have a CREATE SERVER statement in its SQL dialect. The purpose of this statement is to create a connection to another, remote, MySQL server. With that connection you can use the FEDERATED storage engine to access tables in the remote server. Of course, there is no way to run this CREATE SERVER statement unless your program is already connected to a MySQL server.
With respect, your "task which states to create a server at runtime" doesn't make much sense. Is there more to this requirement? What workflow needs this step? Is it part of the installation of some application software on a new box?
I'm a front-end web developer trying to devise a solution to sync a Microsoft Access Database on a local network with a MySQL database on a web server. I ran across some software that might perform this however it looks complicated to maintain and seems like it could be an additional point of failure.
There is also a way MS Access can use an ODBC to an external MySQL database. https://dev.mysql.com/doc/connector-odbc/en/connector-odbc-examples-tools-with-access-linked-tables....
If the ODBC connection to the external MySQL database works, is there a way to sync an external DB table with a local DB table so when a change occurs with one it's pushed to the other?
Or is there another recommendation to handle this process?
Thank you.
I have a situation where I would like a desktop application to be useable whether an internet connection is present or not.
I have a choice of MySQL on a web server and I could work with a local MySQL database or maybe MS Access database on the local drive and then just update data when connection is restored. My issues are as follows.
Sync local changes to remote server. Multi site / multi user scenario so how to keep db in sync when connection restored without loosing changes from other users in server data.
Sync remote changes to local. Multi site / multi user scenario so how to keep db in sync when connection restored without loosing changes made locally while updating with server data.
Currently I am using XML files and LingtoXML querying but it is unsatisfactory to continue with these files so a better solution is required.
Any help would be appreciated to identify what technology would work best and how to keep them in sync.
Thanks in Advance.
"Jet Replication Objects (JRO)", the replication features of the Access Database Engine, have been deprecated (ref: here). I believe that the related management features have also been completely removed from Access 2013. Therefore, native Access replication should no longer be considered a viable option.
Microsoft's recommendation would be to use SQL Server and its replication features. However, SQL Server Express has limitations on how much it can do (e.g., it can be a "Subscriber" but not a "Publisher" or "Distributor", ref: here) so presumably there would have to be a non-free copy of SQL Server involved somehow.
I haven't yet had the occasion to use MySQL replication myself, but it is probably worth considering. Chances are good that you could still use Access as a front-end (via ODBC linked tables).
I've been wondering what are the benefits of using an ODBC driver to interface with a MySQL server? What advantage does that have over directly connecting to the server via TCP and firing off your SQL commands directly?
I'm working with a code base written in labVIEW that references a UDL file which references a data source and its associated ODBC driver to handle the connection to the server. I'm not yet convinced its necessary. I can see the benefit of using a driver if you are connecting to Microsoft Access or excel but if your recipient is an SQL server of some type why would you need a middle man to handle your SQL commands?
I have used the ODBC driver 3.51 for connecting to MySQL Community Server 5.1 for some time now. The ODBC driver allows you (on a Windows computer) to add your MySQL connection to the ODBC data sources list. Now you can reference this data source in many compatible applications. I have been able to use this ODBC connection in VB.Net applications as well as proprietary applications for printing and other functions with ODBC functionality.
I would say that when coding web or python applications i always use the built in MySQL packages, but if you need to access your data through VB.Net or another proprietary application (like a stand-alone windows app) you probably need to set up a system ODBC data source to access your database. To me the ODBC lets Windows access MySQL easily. Without Windows i don't think you need it.
Why ODBC and not JDBC? Some reasons come to mind in order of helpfulness when using JDBC:
Standard api to access the results from a query. To iterate over the results and to get the actual values with the appropriate type.
No need to know how the protocol works to connect to the server. Just use the host, user, password, send the SQL and iterate over the result.
Abstract out the connection to the database. Changing the database should be simpler.
Standard way to commit and rollback for transaction based changes.
In my experience, JDBC is very verbose. You need to write many lines to accomplish simple things. I've found the Spring JDBCTemplate wrapper to be an extremely easy to use alternative for simple stuff.