Microsoft Access Team Blog : Access 2003

Accessing external data using the IN clause

robcooper — Fri, 27 Mar 2009 13:36:00 GMT

Someone sent us a question the other day about one of my favorite dark corners in Access and we thought it might be interesting to dive into this area a little.

Microsoft Access SQL supports two uses of the IN keyword. The most commonly used case is as part of the WHERE clause of a SQL statement to provide a list of values used as criteria. Using the Customers table in the Northwind 2007 sample database as an example, this might look something like:

SELECT [First Name], [Last Name], [State/Province]
FROM [Customers]
WHERE [State/Province] IN ('WA', 'CA', 'NY')

This query returns the names of customers that live in WA, CA, or NY. This keyword provides a nice alternative to the OR clause which would require repeating the field name.

The other use of the IN keyword is as part of the SELECT statement or FROM clause, and is called the IN clause. The IN clause is used to access external data, and can be used in place of linked tables. For example, let's say that you had a SQL Server database that is used as part of an application, but you don't want to maintain a DSN to connect. You could use the IN clause in a query that uses a DSN-less connection to quickly read data from the external table. For example:

SELECT * FROM ExternalTable
IN '' [ODBC;Driver={SQL Server}; Server=ServerName; Database=DatabaseName; Trusted_Connection=Yes]

It is possible to create a linked table that uses a DSN-less connection, but creating the table requires code. Also, unlike a SQL pass-through query, this query is executed by the Access database engine which means that the resultset may also be updateable. Furthermore, there is a certain simplicity or elegance about this technique that I think is cool. Incidentally, there is another syntax for the IN clause, but I prefer this one.

So far so good, but since the IN clause is part of the FROM clause of a query, it can also be used other places where the FROM clause can be used. For example, in a make table query to create a local copy of data in an external table:

SELECT * INTO LocalTable
FROM SourceTable
IN '' [ODBC;Driver={SQL Server}; Server=ServerName; Database=DatabaseName; Trusted_Connection=Yes]

Or, in an append query using the INSERT...INTO statement to move data from the local database into another database. Note that the connection string used in this example is to another Access database.

INSERT INTO DestinationTable (DestinationField)
IN '' [;DATABASE= C:\Users\Rob\Documents\Northwind 2007.accdb]
SELECT SourceField FROM SourceTable

You could even use an append query with multiple IN clauses to concatenate two text files:

INSERT INTO [File2.txt] (Field1)
IN '' [TEXT; FMT=Delimited; HDR=YES; DATABASE= C:\Users\Rob\Documents;TABLE=File2.txt]
SELECT Field1
FROM [File1.txt]
IN '' [TEXT; FMT=Delimited; HDR=YES; DATABASE= c:\Users\Rob\Documents;TABLE=File1.txt];

These are just a few examples of how you could use the IN clause to quickly work with external data. By using different connection strings for the external data sources, you could do some pretty cool stuff.

Dot or Bang?

robcooper — Sat, 31 May 2008 03:39:40 GMT

Here's a question that comes up from time to time. The other day, someone internally asked about the difference between using a dot "." vs. a bang "!" for control references in a form in VBA. In other words, given a form - Form1, with a control - Control1, what are the differences between:

Form1.Control1 ' Control reference using a dot

- and -

Form1!Control1 ' Control reference using a bang

Michael Kaplan was kind enough to respond with the following:

The dot gives you early binding and is resolved at compile time, the bang is resolved at runtime.
In the case of Forms, both controls and fields in the underlying query can be referenced via a dot since they are all in the type library for the form.
Also in the case of Forms, if you change the underlying query at runtime - dot references to the old query's fields will fail at runtime since update of the Form's type library cannot happen at runtime.
Because the dot is early bound, IntelliSense happens by default with the dot, not with the bang.
The dot (since it is early bound) is faster than the bang, but no one runs enough code that uses these items enough for the performance difference to actually matter.

Thanks Michael for responding!

Encryption vs. Encoding

robcooper — Mon, 19 May 2008 23:01:09 GMT

Every now and again we get the question of "what is the difference between encryption and encoding?" This came up again today so we wanted to try to answer it more broadly.

In short, the feature that we call "encryption" is a feature that was introduced for ACCDB files in Access 2007. This feature was an improvement over the feature known as "encoding" in Access 2003. "Encoding" uses a proprietary algorithm for scrambling the data in a database and was first introduced in Access 2.0. "Encryption", used in Access 2007, uses improved Windows APIs and is stronger than previous versions.

In addition to the algorithm being used, here's a summary of the functional differences:

	Encryption	Encoding
File format	ACCDB, ACCDE, ACCDA	MDB, MDE, MDA
Requires database password?	Yes	No
Creates a new file?	No	Yes
Ribbon entry point	"Encrypt with Password"	"Encode/Decode Database"
Requires the database to be opened exclusively?	Yes (because a database password is required)	No

You'll notice that a database password is required when using "encryption" in a database in the ACCDB file format and not in the MDB file format. As a result, the behavior of these buttons is different in the Ribbon. When you click "Set Database Password" in the Ribbon in an MDB file, a database password is opened, but the file is not encoded. We've changed the text of the command in an ACCDB file to read "Encrypt with Password" to demonstrate that these are in fact a single operation.

The feature called "encoding" in Access 2003 and Access 2007 was previously called "encryption" in Access 2002 and earlier. We realize this is somewhat confusing, however, the term "encoding" more accurately describes the algorithm used for the feature so we changed it in Access 2003. Databases encoded using Access 2003 or earlier should not be considered secure.

If you're working with both the MDB and ACCDB file formats in Access 2007, there are a few things to keep in mind:

An encoded MDB database cannot be converted to the ACCDB file format
An encrypted ACCDB cannot be converted to the MDB file format
Because encrypted databases cannot be converted to MDB files, you'll need to remove the database password to save an encrypted ACCDB as an MDB

Lastly, we'd love to hear more from you about this. How many of you are using encryption in ACCDB files vs. encoding in MDB files? Thanks!

Access Source Code Control and Team Foundation Server

robcooper — Thu, 15 May 2008 03:35:27 GMT

Today's guest writer is Mike Sullivan - a tester on the Access team

With the release of Visual Studio Team System 2008, we've recently received questions from several customers regarding whether or not Team Foundation Server (TFS) can act as a source code control provider for the Access source code control (SCC) component. The answer is yes!

Although many folks refer to Access’ source code control component as “SourceSafe integration,” that only tells part of the story. SCC integration within Access is fully compatible with any provider that implements the Microsoft Source Code Control Interface (MSSCCI). Although Visual SourceSafe is one of the more widely used MSSCCI providers, there are several other products that implement this interface, including Team Foundation Server 2005 & 2008 as well as IBM ClearCase.

However, MSSCCI support in Team Foundation Server is not native and requires an additional add-in available for download:

MSSCCI Add-in for Team Foundation Server 2005
MSSCCI Add-in for Team Foundation Server 2008

Of course, to enable SCC functionality from within Access, you’ll also need the Source Code Control add-in. This shipped as a free download as a part of the Access Developer Extensions for Access 2007 and as a separate free add-in for Access 2003:

Access 2007 Developer Extensions
Access 2003 Source Code Control Add-in

If you’re interested in taking this configuration for a whirl, you might want to download the Team Foundation Server Virtual PC image that has been made available by the Visual Studio team. Included on this virtual PC are copies of Visual Studio Team System 2008 and Office 2007 Enterprise SP1 (though Access is not installed by default on this image – you’ll need to go to Add/Remove programs within Control panel and launch setup to install Access). This trial image is good through December 31, 2008.

To get the Virtual PC image working, you’ll also need to install the Access Developer Extensions (the MSSCCI add-in is preinstalled). Since VSS is the default MSSCCI provider on the machine, you’ll need to tweak a registry key to get Access to use Team Foundation instead:

Path: HKEY_LOCAL_MACHINE\SOFTWARE\SOURCECODECONTROLPROVIDER
Key: ProviderRegKey
Value: SOFTWARE\Microsoft\Team Foundation Server MSSCCI Provider

Hopefully those of you curious about support for TFS have had your questions answered!

Microsoft Access Downloads in Silverlight

Zac Woodall — Mon, 21 Jan 2008 20:45:40 GMT

I ran across this new Silverlight version of the Microsoft download center this morning. If you haven't seen Silverlight yet, it is pretty cool stuff. It is Microsoft's engine for doing rich graphics composition in the web. Here are all the downloads Microsoft has in the download center which are Access related.

UI Builder for Access v.3.0 Released

Zac Woodall — Fri, 11 Jan 2008 23:27:55 GMT

Brandon Smith-Daigle has recently released the 3.0 update for his UI Builder tool that helps Access developers to build customized user experiences in Forms without coding the VBA themselves. This tool is compatible with older versions of Access as well as 2007. He's running a limited time 25% discount until the end of Jan. Thanks Brandon for the pointer!

Goldsoft tools for Access Developers

Zac Woodall — Fri, 11 Jan 2008 20:27:39 GMT

Ken Hockley has recently released his Goldsoft suite. These tools aim to increase Access developer productivity by helping to reduce the amount of time spent building necessary application plumbing so that developers can focus their effort on producing business logic. More info is available at Ken's Goldsoft website. Thanks Ken for the pointer!

Access 2003 SP3 hotfix rollup now available

Clint Covington — Fri, 28 Dec 2007 12:35:00 GMT

You can find details here...

http://support.microsoft.com/kb/945674

[Zac] For those of you who are wondering, this is the update I've told several folks would be coming. Everyone who is running Access 2003 SP3 will probably want to apply this patch. It includes fixes for the known problems SP2 users had when upgrading to SP3. We intend to eventually roll this out through Windows Update, but for now, the only way to get these fixes is to download and apply this patch on top of 2003 SP3.