VB.NET: SQLite to SQL Server - sql-server

I have a vb.net project that uses a SQLite database. I do this by using dataset/table adapters. The client is happy and all works well. However I have just heard that they plan on providing this product to another customer that wishes to use their SQL Server database. So I am writing this post so I can mentally prepare for this before I begin. I am not a database pro and have really enjoyed the simplicity of setting up and managing an SQLite database.
So any ideas on the easiest way to support SQL Server as well? I am happy to run them parallel to each other. Can I just make a separate service / middleware that syncs the SQLite database to the SQL Server on a timer and does not care about what the main app is up to?
Any pointers are appreciated.

Synchronizing two databases is possible, if rather complex. You need some mechanism to find out which records have changed, and if it is possible to have new changes in both databases, you also have to resolve conflicts.
A timer-based approach doesn't sound efficient: in most cases, the timer doesn't have anything to do; and after some data change, there is some amount time where the databases are not synchronized.
Can't you just replace SQLite with MS SQL Server?
I.e., have some configuration settings that determines whether your program's data lies in SQLite or on a server?
Assuming that an SQL Server database with the required structure already exist, this would, in theory, need nothing more than a changed connection string, and supplying some user name/password (if the server isn't configured to automatically use Windows logins).
There shouldn't be any big differences in the SQL dialects used. You have, of course, to test all your queries.

Related

Are there alternatives to ODBC for MS Access/SQL Server Connection?

My question is this: Are there alternatives to ODBC that would allow us to connect our SQL Server to MS Access?
Here's the situation: My company works with a proprietary, SQL database (ProVenue) that up and decided to "no longer support ODBC" to MS Access, our front-end tool, without telling us.
We are currently migrating away from ProVenue, but in the meantime , we're stuck with a vendor, which "no longer supports" our ODBC connection(s). The vendor also has no incentive to help since we're leaving in several months.
I've devised a workaround where I manually export the ProVenue tables (ASCII), proof (yes, the export utiliy pulls unreliably), convert and upload on a daily basis into Access. That said, it is unreasonably time consuming given the number of tables. This work-around could be a full-time job.
Do you know of any alternatives?
Do NOT consider using ADP. It has been dropped from Access 2013 and hence is a technology with no future.
From what you're saying, you don't "own" your own MSSQL database - you're simply connecting to an instance that the provider manages, correct? I would guess that they've disabled ODBC connections to MSSQL because they don't like the load placed on their servers and/or that they've decided they want to change some underlying structures and don't want to have to cope with anybody whining about those changes.
That said, do they allow direct MSSQL connections? Via SQL Management Studio, for example? If so, you should be able to define an export & import process which is less buggy than theirs, and simply re-point your Access database to the local copy of data. True, this would still require some (possibly automated) import process, so you'd be out of synch with the server, but it'd give you the solution.
You might try connecting an .adp file to the server, to see if they'll still let you access things in that manner. That would possibly require significant modifications to your Access solution, but would also be a bit easier on their servers than linked tables via ODBC.
You could have a look at Access Data Projects (ADP) which are tied directly to one SQL Server database. I don't think they use ODBC at all, but they have their own limitations, and of course, aren't available in older Access versions.

Entity Framework, No SQL server, What do I do?

Is there seriously no way of using a shared access non-server driven database file format without having to use an SQL Server? The Entity Framework is great, and it's not until I've completely finished designing my database model, getting SQL Server Compact Edition 4.0 to work with Visual Studio that I find out that it basically cannot be run off a network drive and be used by multiple users. I appreciate I should have done some research!
The only other way as far as I can tell is to have to set up an SQL server, something which I doubt I would be able to do. I'm searching for possible ways to use it with Access databases (which can be shared on a network drive) but this seems either difficult or impossible.
Would I have to go back to typed DataSets or even manually coding the SQL code?
Another alternative is to try using SQL
Install SQL Server express. Access is not supported by EF at all and my experience with file based databases (Access, SQL Server CE) is mostly:
If you need some very small mostly readonly data to persist in database you can use them (good for code tables but in the same time such data can be simply stored in XML).
If you expect some concurrent traffic and often writing into DB + larger data sets their performance and usability drops quickly. They are mostly useful for local storage for single user.
I'm not sure how this relates for example to SQLite. To generate database from model for SQLite you need special T4 template (using correct SQL syntax).
Have you tried SQLite? It has a SQL provider, and as far as I know EF supports any provider. Since it's file-based, that might be a plausible solution. It's also free.

Suitable method For synchronising online and offline Data

I have two applications with own database.
1.) Desktop application which has vb.net winforms interface, runs in offline enterprise network and stores data in central database [SQL Server]
**All the data entry and other office operations are carried out and stored in central database
2.) Second application has been build on php. it has html pages and runs as website in online environment. It stores all data in mysql database.
**This application is accessed by registered members only and they are facilitied with different reports of the data processed by 1st application.
Now I have to synchronize data between online and offline database servers. I am planning for following:
1.) Write a small program to export all the data of SQL Server [offline server] to a file in CVS format.
2.) Login to admin Section of live server.
3.) Upload the exported cvs file to the server.
4.) Import the data from cvs file to mysql database.
Is the method i am planning good or it can be tunned to perform good. I would also appreciate for other nice ways for data synchronisation other than changing applications.. ie. network application to some other using mysql database
What you are asking for does not actually sound like bidirectional sync (or movement of data both ways from SQL Server to MySQL and from MySQL to SQL Server) which is a good thing as it really simplifies things for you. Although I suspect your method of using CSV's (which I would assume you would use something like BCP to do this) would work, one of the issues is that you are moving ALL of the data every time you run the process and you are basically overwriting the whole MySQL db everytime. This is obviously somewhat inefficient. Not to mention during that time the MySQL db would not be in a usable state.
One alternative (assuming you have SQL Server 2008 or higher) would be to look into using this technique along with Integrated Change Tracking or Integrated Change Capture. This is a capability within SQL Server that allows you to determine data that has changed since a certain point of time. What you could do is create a process that just extracts the changes since the last time you checked to a CSV file and then apply those to MySQL. If you do this, don't forget to also apply the deletes as well.
I don't think there's an off the shelf solution for what you want that you can use without customization - but the MS Sync framework (http://msdn.microsoft.com/en-us/sync/default) sounds close.
You will probably need to write a provider for MySQL to make it go - which may well be less work than writing the whole data synchronization logic from scratch. Voclare is right about the challenges you could face with writing your own synchronization mechanism...
Do look into SQL Server Integration Service as a good alternate.

how to automate upsizing from Access to SQL Server?

I need to automate the migration from an Access (2003) to an SQL Server DB (2005 or 2008). The upsizing should be done automatically as part of a build process.
I need that because there are 2 versions of the software, a single user rich client and a web version. Access DB is used for single user to minimize setup effort, SQL Server to improve performance and scaling with many simultanious users. Access should be the "leading" DB, meaning devs do changes in Access DB and those are propagated to the SQL server within the build process. Many changes will occur, so doing it manually is not an option.
I am new to the Microsoft world, so I dont know appropriate tools for that. What tools can I use and how? I know how to do it (by clicking) with the upsizing assistant. Perhaps I can automate that somehow?
Thanks in advance for your answers.
Cheers,
Arne
Why not use a SQL Server backend for The Access database? Then changes are only made once and all is in synch.
The problem here is that you trying to do versing with two different systems.
If all of the design changes can be done in Access, then you can simply up-size that to sql server. The problem here is do you need to modify the existing sql server databases? And, do you need this over time? Upsizing the access database will get the new version up to sql server, but it WILL NOT help for existing sql server databases.
If you need over time to have changes to tables on BOTH systems and existing systems then I would state to the access developers that ALL changes to the tables MUST be written as ddl sql. You then use the ddl executed on Access to make the changes. The developer MUST THEN AT THAT POINT take that same ddl and run it on the sql side. It might need slight modifications. They fix it to run on sql server. So, then you wind up with two scripts. One for sql server, and one for Access. In the case of access you can write a few lines of code to read and process a text file of ddl. (that same code can be used for all scripts).
That way, you build up a equivalent set of changes for each upgrade. So, simply NEVER allow design changes direct to the access tables. If you allow design changes with the table designer then you are in big trouble as you don't now know what changes need to be carried over to sql server.
However, as better recommend approach I would suggest that table desing changes are done FIRST in sql server. The reason is the table designer in sql visual studio tools allow the changes just made to be scripted to the clipboard (a simple right click). The other reason is that the table designer is VERY much like the access one. So, this is easy even for access developers with little sql server experience to use. So, that simple right click of "script changes to clip board" would create the need change script for sql server (they would save this into a file for sql server). They then take the ddl, and run it on the access side. The reason for this is the ddl might need some slight mods for Access (but, they did not have to write the ddl statement). So, this means the ddl gets written for them. This means you know the sql server ddl is correct. They then simply take that ddl and use again to change the access table also. The ddl might need slight changes for access, but that's just fine because they need the table change and then run and fix this untill the simple table change is made. So this scripted ddl would be then saved for the access update into a file also. The ddl script might need slight modifications for access so I think this approach is best. As long as this is being changed/fixed as they go along you be fine.
So over a period of changes, you wind up with two scripts that keep the changes in sync for both systems.
If you don't need changes to existing sql and access databases, then just let the access folks have at it, and then simply up size the whole database to sql server in one shot and you done.
I can't really think much of any other approach between the above two extremes.
You could have the users make the change in access and then go to sql server to make the change in the sql table design and then save the sql server change script. However, this would not get you a change script for the access side. If a change script is NOT needed for access side then this would work very well as you would get a sql server change script.
The above would be how I go about this and it quite workable...

MS Access Application - Convert data storage from Access to SQL Server

Bear in mind here, I am not an Access guru. I am proficient with SQL Server and .Net framework. Here is my situation:
A very large MS Access 2007 application was built for my company by a contractor.
The application has been split into two tiers BY ACCESS; there is a front end portion that holds all of the Ms Access forms, and then on the back end part, which are access tables, queries, etc., that is stored on a computer on the network.
Well, of course, there is a need to convert the data storage portion to SQL Server 2005 while keeping all of these GUI forms which were built in Ms Access. This is where I come in.
I have read a little, and have found that you can link the forms or maybe even the access tables to SQL Server tables, but I am still very unsure on what exactly can be done and how to do it.
Has anyone done this? Please comment on any capabilities, limitations, considerations about such an undertaking. Thanks!
Do not use the upsizing wizard from Access:
First, it won't work with SQL Server 2008.
Second, there is a much better tool for the job:
SSMA, the SQL Server Migration Assistant for Access which is provided for free by Microsoft.
It will do a lot for you:
move your data from Access to SQL Server
automatically link the tables back into Access
give you lots of information about potential issues due to differences in the two databases
keeps track of the changes so you can keep the two synchronised over time until your migration is complete.
I wrote a blog entry about it recently.
You have a couple of options, the upsizing wizard does a decent(ish) job of moving structure and data from access to Sql. You can then setup linked tables so your application 'should' work pretty much as it does now. Unfortunately the Sql dialect used by Access is different from Sql Server, so if there are any 'raw sql' statements in the code they may need to be changed.
As you've linked to tables though all the other features of Access, the QBE, forms and so on should work as expected. That's the simplest and probably best approach.
Another way of approaching the issue would be to migrate the data as above, and then rather than using linked tables, make use of ADO from within access. That approach is kind of famaliar if you're used to other languages/dev environments, but it's the wrong approach. Access comes with loads of built in stuff that makes working with data really easy, if you go back to use ADO/Sql you then lose many of those benefits.
I suggest start on a small part of the application - non essential data, and migrate a few tables and see how it goes. Of course you back everything up first.
Good luck
Others have suggested upsizing the Jet back end to SQL Server and linking via ODBC. In an ideal world, the app will work beautifully without needing to change anything.
In the real world, you'll find that some of your front-end objects that were engineered to be efficient and fast with a Jet back end don't actually work very well with a server database. Sometimes Jet guesses wrong and sends something really inefficient to the server. This is particular the case with mass updates of records -- in order not to hog server resources (a good thing), Jet will send a single UPDATE statement for each record (which is a bad thing for your app, since it's much, much slower than a single UPDATE statement).
What you have to do is evaluate everything in your app after you've upsized it and where there are performance problems, move some of the logic to the server. This means you may create a few server-side views, or you may use passthrough queries (to hand off the whole SQL statement to SQL Server and not letting Jet worry about it), or you may need to create stored procedures on the server (especially for update operations).
But in general, it's actually quite safe to assume that most of it will work fine without change. It likely won't be as fast as the old Access/Jet app, but that's where you can use SQL Profiler to figure out what the holdup is and re-architect things to be more efficient with the SQL Server back end.
If the Access app was already efficiently designed (e.g., forms are never bound to full tables, but instead to recordsources with restrictive WHERE clauses returning only 1 or a few records), then it will likely work pretty well. On the other hand, if it uses a lot of the bad practices seen in the Access sample databases and templates, you could run into huge problems.
It's my opinion that every Access/Jet app should be designed from the beginning with the idea that someday it will be upsized to use a server back end. This means that the Access/Jet app will actually be quite efficient and speedy, but also that when you do upsize, it will cause a minimum of pain.
This is your lowest-cost option. You're going to want to set up an ODBC connection for your Access clients pointing to your SQL Server. You can then use the (I think) "Import" option to "link" a table to the SQL Server via the ODBC source. Migrate your data from the Access tables to SQL Server, and you have your data on SQL Server in a form you can manage and back up. Important, queries can then be written on SQL Server as views and presented to the Access db as linked tables as well.
Linked Access tables work fine but I've only used them with ODBC and other databases (Firebird, MySQL, Sqlite3). Information on primary or foreign keys wasn't passing through. There were also problems with datatype interpretation: a date in MySQL is not the same thing as in Access VBA. I guess these problems aren't nearly as bad when using SQL Server.
Important Point: If you link the tables in Access to SQL Server, then EVERY table must have a Primary Key defined (Contractor? Access? Experience says that probably some tables don't have PKs). If a PK is not defined, then the Access forms will not be able to update and insert rows, rendering the tables effectively read-only.
Take a look at this Access to SQL Server migration tool. It might be one of the few, if not the ONLY, true peer-to-peer or server-to-server migration tools running as a pure Web Application. It uses mostly ASP 3.0, XML, the File System Object, the Data Dictionary Object, ADO, ADO Extensions (ADOX), the Dictionary Scripting Objects and a few other neat Microsoft techniques and technologies. If you have the Source Access Table on one server and the destination SQL Server on another server or even the same server and you want to run this as a Web Internet solution this is the product for you. This example discusses the VPASP Shopping Cart, but it will work for ANY version of Access and for ANY version of SQL Server from SQL 2000 to SQL 2008.
I am finishing up development for a generic Database Upgrade Conversion process involving the automated conversion of Access Table, View and Index Structures in a VPASP Shopping or any other Access System to their SQL Server 2005/2008 equivalents. It runs right from your server without the need for any outside assistance from external staff or consultants.
After creating a clone of your Access tables, indexes and views in SQL Server this data migration routine will selectively migrate all the data from your Access tables into your new SQL Server 2005/2008 tables without having to give out either your actual Access Database or the Table Contents or your passwords to anyone.
Here is the Reverse Engineering part of the process running against a system with almost 200 tables and almost 300 indexes and Views which is being done as a system acceptance test. Still a work in progress, but the core pieces are in place.
http://www.21stcenturyecommerce.com/SQLDDL/ViewDBTables.asp
I do the automated reverse engineering of the Access Table DDLs (Data Definition Language) and convert them into SQL equivalent DDL Statements, because table structures and even extra tables might be slightly different for every VPASP customer and for every version of VP-ASP out there.
I am finishing the actual data conversion routine which would migrate the data from Access to SQL Server after these new SQL Tables have been created including any views or indexes. It is written entirely in ASP, with VB Scripting, the File System Object (FSO), the Dictionary Object, XML, DHTML, JavaScript right now and runs pretty quickly as you will see against a SQL Server 2008 Database just for the sake of an example.
It takes perhaps 15-20 seconds to reverse engineer almost 500 different database objects. There might be a total of over 2,000 columns involved in this example for the 170 tables and 270 indexes involved.
I have even come up with a way for you to run both VPASP systems in parallel using 2 different database connection files on the same server just to be sure that orders entered on the Access System and the SQL Server system produce the same results before actual cutover to production.
John (a/k/a The SQL Dude)
sales#designersyles.biz
(This is a VP-ASP Demo Site)
Here is a technique I've heard one developer speak on. This is if you really want something like a Client-Server application.
Create .mdb/.mde frontend files distributed to each user (You'll see why).
For every table they need to perform an CRUD, have a local copy in the file in #1.
The forms stay linked to the local tables.
Write VBA code to handle the CRUD from the local tables to the SQL Server database.
Reports can be based off of temp tables created from the SQL Server (Won't be able to create temp tables in mde file I don't think).
Once you decide how you want to do this with a single form, it is not too difficult to apply the same technique to the rest. The nice thing about working with the form on a local table is you can keep a lot of the existing functionality as the existing application (Which is why they used and continue to use Access I hope). You just need to address getting data back and forth to the SQL Server.
You can continue to have linked tables, and then gradually phase them out with this technique as time and performance needs dictate.
Since each user has their own local file, they can work on their local copy of the data. Only the minimum required to do their task should ever be copied locally. Example: if they are updating a single record, the table would only have that record. When a user adds a new record, you would notice that the ID field for the record is Null, so an insert statement is needed.
I guess the local table acts like a dataset in .NET? I'm sure in some way this is an imperfect analogy.

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