Visual Basic 6 Black Book:Databases: Using DAO, RDO, And ADO
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Connecting A Data Control To A Bound Control
In the previous few topics, we connected a database to a data control. To see that data, we’ll use a data-bound control—a text box. We’ll investigate all the data-bound controls later in this chapter—after we’ve gone through the ways of connecting to databases—so this is just to get us started.

To connect a text box to a data control, set the text box’s DataSource property to the name of the data control (or remote data control or ADO control). To display a particular field in the text box, place that field’s name in the text box’s DataField property.
Let’s see an example. Here, we’ll use the database, db.mdb, and the data control we’ve developed over the previous few topics. Add a text box, Text1, to the program now and set its DataSource property to Data1. When you move through the database with the data control, the data control will hold the current record; to display a field in the current record, place that field’s name in the text box’s DataField property; here, we’ll place the Name field in that property.

TIP:  Set the text box’s DataSource and DataField properties after adding and connecting the data control. When you do, you’ll find the text box’s DataSource and DataField properties can be set with drop-down list boxes in the Properties window, making that process easier.

When we run the program, we get the result in Figure 24.9. Using the data control, you can move to the beginning or end of the database, and step through record by record as well. Congratulations—now you’re working with databases. The code for this example is located in the dao folder on this book’s accompanying CD-ROM.


Figure 24.9  Using a data control to move through a database.
Registering An ODBC Source
The Testing Department is calling again. Your program with the data control, SuperDuperDataBase, is terrific, but what if you want to work with an ODBC database? Hmm, you think, is that possible?
It is, with the remote data control. You can use an ODBC data source with a remote data control, but first you have to configure a new connection for the ODBC source. You configure an ODBC connection with the 32-bit ODBC item in your computer’s control panel. Open that item now, click the System DSN tab (DSN stands for data source name), and click the Add button to open the Create New Data Source dialog box you see in Figure 24.10.

Figure 24.10  The Create New Data Source dialog box.
You can see the ODBC drivers installed on your system in this dialog box. Select the one you want to use and click Finish; to install the db.mdb file we’ve developed in the previous few topics, we’ll select the Microsoft Access Driver entry here.

This opens the ODBC Microsoft Access dialog box you see in Figure 24.11. Use the Select button to select the database file, db.mdb in our example, and click on the OK button in the ODBC Microsoft Access dialog box. We give the name db to this source.

Figure 24.11  The ODBC Microsoft Access dialog box.
This creates a new ODBC connection for our file, and that connection appears in the ODBC Data Source Administrator, as shown in Figure 24.12.


Figure 24.12  The ODBC Data Source Administrator.
Click on the OK button to close the ODBC Data Source Administrator. Now you’ve added a new ODBC source to your computer’s data environment. We’ll use this data source, db, in the next topic.
Opening A Database With A Remote Data Control
To add a new remote data control to a form, follow these steps:


1.  Select the Project|Components menu item.
2.  Click the Controls tab in the Components dialog box that opens.
3.  Select the Microsoft Remote Data Control entry in the Controls list box.
4.  Click on OK to close the Components dialog box.
5.  This adds the Remote Data Control tool to the toolbox; draw that control as you want it on your form.
6.  Connect the remote data control to an ODBC data source with the DataSource property.
7.  Create a result set (unlike data controls and ADO data controls, which use record sets, remote data controls use result sets) that you can work with by supplying an SQL statement in the SQL property.

Let’s see an example. Add a remote data control, MSRDC1, to a form now. We’ll connect it to the db ODBC data source we’ve created in the previous few topics, and you do that by setting the remote data control’s DataSourceName property to “db”.
Unlike the data control or the ADO data control, you need to create a result set to work with in the remote data control, and we create a result set by selecting the entire students table with the SQL statement SELECT * FROM students. Place that string in the control’s SQL property.
Now we’ve connected our database to the remote data control—but how do we connect the remote data control to bound controls? We’ll look at that in the next topic.



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