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.
Related
I have a series of Access 2002 "Front-end/Back-end" applications all related to each other. For example, application A has linked tables with application B and vice versa.
The applications are at a stage where daily compaction and repair is required due to the volume and high level of corruption. Moreover, to be able to make the applications work properly, I must make the changes in a virtual environment with Access 2002. I also need to reinstall "Access runtime 2010 - 32bits" and copy the Access files (.mde) on every workstation (Windows 10) every time I am making a change in the applications.
#Gustav This is a temporary option (6 months to 18 months) because the customer would like to go to a complete solution with SQL database. The studied solution is configurable and already has a SQL database schema.
I have already done the test to transfer forms, tables, queries and modules to Access 365 but I have errors in the VBA code. All business rules are coded in the VBA code. I also did the transfer of the tables to SQL Server 2017 but I'm afraid I will have to change a lot of VBA code because of the disuse of the DAO engine in the Access 365 front-end.
In fact, to be clearer, I wonder about the need to change the front end to Access knowing that it is a temporary solution.
Maybe, I should keep the software under respirator by eliminating data history in large tables. The time the client takes their decision. Find the "sweet spot" that would allow me to erase and continue to maintain it without having to worry about corruptions because I have a hard time seeing a substantial gain in the migration to the Access 365 front-end. What do you think?
I have already proposed to migrate applications and tables in the new version of to Access 2019 and even moving on SQL Server. However, for now, I must put the application on the respirator and continue the daily compaction until a decision is made.
I would like to know if there is a gain to migrate from Access 2002 to the Access 2019 version knowing the total limit of 2 GB Access. What are the major constraints he would have to migrate to a SQL database knowing that the VBA application and code uses the DAO method?
#Albert D. Kallal
I really like your answer. I should come to a decision soon.
However, I have 2 additional questions. Perhaps, could you guide me on the subject.
There are two things that have recently came to haunt the tranquility that reigned over these applications.
1- For a unknown reason, one of the applications that was part of the swarm of Access applications was blocked for some time with these errors 'Runtime 3027: Cannot update: Database or object is read only'. The problem is that some users have ignored this error and continue their tasks which caused a data shift.
I had to go back with backup copy because some tables were not updated.
Looking more closely at the error in the VBA code I noticed that it all came from the DAO Recordset.Edit method containing queries with multiples joins.
I managed to work around this problem by modifying the Edit method with DoCmd.RunSQL and by changing the query from a Select to an Update query.
However, the whole method worked perfectly well before.
Can you explain to me the cause of this error?
2- The original developer did not necessarily use best practices for the design of the application (no autonumber, some tables without primary key, no foreign keys) so I'm afraid that a new design will need to be done if I migrate to a SQL Server database. Or maybe to save time, as this solution is going to disappear in 18 months, I should only replicate the bad practices in SQL Server and pray that it does not cause any more glitches. What would be your professional approach?
Thank you
There may be none. Open the database in Access 2019/365 and save it in the 2007 (accdb) format, and check it out.
As for the distribution, you can make this fully automatic using a script and a shortcut. It is explained in full in my article:
Deploy and update a Microsoft Access application with one click
If you don't have an account, browse to the link: Read the full article.
Push hard to get a confirmation on the move of all the shared tables to an SQL Server backend.
A few things:
To update your mde or accDE front end? That is a simple copy to each workstation. You don’t need to re-install the runtime each time. There is no “special” connection between one particular application (mde/accde) that you deploy to each workstation.
In other words:
If you writing software in VB6, then you need to install the VB6 run time (but only one time). After that you can simply copy + deploy your application to each workstation.
If you writing software in say .net then again, you have to ensure the correct .net framework is installed on each computer. Once done, then again you can update your software by a simple copy to each workstation.
And the same goes for using the access run time. Once installed, then you can simply copy any mde/accDE to that workstation, double click on it and it will run. So the run time is not connected to any particular database you copy to the workstation. Once you have the runtime installed, then you can rather easy cook up some automatic update code for the front end to "check" some version number, and then copy down the new updated front end. There are quite a few ways to do this - even a simple batch file can often suffice here.
So in near all cases these days, you will have to do “one time” install of the required run-time and support libraries. This is the case for .net, older VB6 programs, or Access.
As for migration of the access table data to SQL server?
You should be able to simply migrate the table data to SQL server. Now link the application tables from the older access back end to SQL server.
At this point, 99% of your VBA and even DAO recordset code should work just fine.
There is no need (or even a good reason) to dump using DAO code you have – it should work as before with VERY few modifications.
About the only change is for code that does this:
Dim strSQL As String
Dim rst As DAO.Recordset
strSQL = "select * from tblCustomers where City = 'Edmonton'"
Set rst = CurrentDb.OpenRecordset(strSQL)
' above for SQL server becomes:
Set rst = CurrentDb.OpenRecordset(strSQL, dbOpenDynaset, dbSeeChanges)
And you can even migrate the tables with indexes, and table relationships intact by using the Sql Server Migration Assistant for Access (SSMA). You can find this fantastic tool here:
https://www.microsoft.com/en-us/download/details.aspx?id=54255
So, about 99% of existing forms and VBA code will work as before after you migrate the data to SQL server.
I am having to develop an application very rapidly. I have chosen SQL Server (2012) as the DB backend, and I will write all my stored procs, triggers etc in the backend.
However, for UI (logon, reporting etc), I am using Access 2010 for the frontend. I am new to both Access used earlier versions of Access waaay back in the day) and SQL Server (familiar with other Db's).
The goal is to have the database reside on a server and let clients connect with an instance of Access 2010 running locally on their machine.
I am looking for a quick tutorial that shows me how to use the SQL server objects from the Access frontend (I believe its called linking) - any link to useful resource would be very helpful, as I can't seem to locate anything useful (I may searching using the wrong keywords).
Assuming you built all the tables and data on SQL server, then in Access it is a simple matter to link Access to that database.
And to save development time, you can continue to use the Access simple approach of using forms bound to those tables. As long as you launch a form with some kind of criteria (say an invoice number), then that bound form will ONLY pull down the one record from SQL server into that form. (so need to write or use store procedures etc. for that form). And any triggers etc. you have built in SQL server will run without you having to do anything from the Access side.
So a plane jane form build in Access that is bound to a table of say 1 million rows in Access does not need any “special” code – just make sure you launch the form with the “where” clause that Access provides and the form will only pull + load the one record.
So 99% of the normal development process you used in Access in the past will continue to work. Using SQL server for the most part does not change much if anything in regards to building forms that edit such data.
However, for reports and some forms that query + search for data etc., or some VBA code that needs to “process” data, you are most free to call store procedures. You simply create a pass-through query in Access. The VBA code to use that T-SQL thus looks like this:
Currentdb.QueryDefs("MyRawt-sqlPassThoughquery").Execute
Or
with CurrentDb.QueryDefs("MyPass")
.SQL = "exec sp_myProc"
.Execute
end with
In the past for most access applications you likely used liked tables – those linked tables can be to a Access file (back end), or Oracle, or SQL server – how the actual application works and functions is really much the same for all cases. (so there not really a lot of “specific” things you need to know from the Access side – if you comfortable with Oracle, or SQL server, then using Access as a front end works just fine, and the typical development approaches used in Access will remain typical.
Here is an article that outlines the linking process:
https://support.office.com/en-us/article/Import-or-link-to-SQL-Server-data-A5A3B4EB-57B9-45A0-B732-77BC6089B84E?ui=en-US&rs=en-US&ad=US&fromAR=1
Keep in mind you will see MANY articles that talk about ADP projects - they have been deprecated since Access 2010, and I don't recommend using ADP projects with Access - so be careful, since many articles that talk about Access + SQL server are built around ADP projects which as noted should not be used anymore.
This office.microsoft.com article should give you a good overview.
With plenty of more technical information searching for "query sql server from ms access".
Don't mess about with linked tables. Use an Access ADP (Access data project), which is natively connected to SQL Server. Sadly this type of access file is being phased out but it is the optimal solution for an MS Access front end with a SQL Server back end
Pros and Cons of Access Data Project (MS Access front end with SQL Server Backend)
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.
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.
I m using Access 97 database.It has lots of forms. Data bulked. I have to upgrade it quickly. I bought SQL Server 2005 enterprise edition.
I want to use SQL Server for data holder. I m going to use Access forms regularly. I just want to export data to the sql server.
Is it possible to use "Linked" data storing?
While I agree with HLGEMs first paragraph I respectfully disagree with HLGEMs second paragraph. There are quirks you need to know about of which I'm somewhat ignorant. Such as changing boolean fields to LittleInt. But otherwise it's a lot of tedious work to recreate the database schema. And it'll be error prone such as missing indexes or relationships.
There is a tool from the SQL Server group which is a lot better than the Upsizing Wizard especially the Access 97 version.
SQL Server Migration Assistant for Access (SSMA Access)
http://www.microsoft.com/sql/solutions/migration/access/default.mspx
As you discover these quirks you can change the scripts to recreate the database with the appropriate changes.
I concur with Tony Toews (and you should trust him on this, he's an Access guru): use SSMA to help you move data to SQL Server, it does a more complete job than the upsizing Wizard integrated in Access (which doesn't work for upsizing to SQL Server 2008 anyway).
You have to be wary of a few caveat though; I've made a blog post about some of the things you should check out.
The point is that if the original Access database was designed without relying too much on the liberties that Access allows (strange characters in table and column names for instance), then the process will be much easier.
Pay special attention to all the warning and errors reported by SSMA, they are really useful in helping you focus on the issues you must solve.
With regards to performance, moving to SQL Server isn't necessarily going to make things faster.
In some areas it will actually be slower, sometimes much much slower:
Access is pretty good at optimizing certain forms of data access but once the database moves outside of its reach, it doesn't have as much control.
Most things will work fine though.
You will probably have to rewrite a few queries, maybe move them as views on SQL Server instead of keeping them in your Access application.
Little things such as using % instead of * as wildchars in queries using LIKE in their WHERE clause can also cause strange issues like queries not returning any records.
By the way, I'll post a very good resource Tony has on his own website regarding SQL upsizing: My random thoughts on SQL Server Upsizing from Microsoft Access.
There is also a good and detailed read about things to consider when using SQL Server from Access: Optimizing Microsoft Office Access Applications Linked to SQL Server
YOu can add the SQL Server tables to access as linked tables. Then you will want to start looking at your slowest queries and convert them to stored procs.
Do not use the upgrade wizard in Access to create the SQl Server tables becasue it will make poor choices for datatypes. Do the work yourself to create the scripts, choosing the best datatypes. It takes longer this way, but your database will perform better and you will gain a better understanding of how to do things in SQL Server. You should start right now, learning to do everything through a script and never from the GUI. Best to learn good habits in SQL Server from the start.