sample code to connect SQL database using VB6

Posted on 2000-04-03
Last Modified: 2010-08-05

How many ways to make connection from VB6 to SQL database?

Is there any sample code ?

I'm using Win95 and SQL server 7.

Question by:isman
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Expert Comment

ID: 2682439
WELL It depends. YOu can use iether OLEDB PROVIDER OR ODBC. Connection can be iether though DSN or DSNLESS. However you prefer. Here are some samples.

ex using DSN.
DIM CN as New ADODB.Connection
cn.ConnectionString = "DSN=" & _
cn.connectionstring="DRIVER=SQL SERVER" & _
ex of OLEDB

LVL 14

Expert Comment

ID: 2682519
As Marine so correctly points out.. ADO is the preferred way to go.. <smile>. Although the documentation is not the best (at least on my CD version of MSDN 4/99), you may also want to try using the Data Environment Designer (Vb Menu -> Project -> Add Data Environment). It is a graphical interface for building ADO connections, commands, recordsets, SQL statements and features a Data Viewer. Its only downside, as I stated earlier, is the documentation that accompanies it.. <sigh>. Oh well.. such is life in the VB fast lane.. <smile>.

LVL 28

Expert Comment

ID: 2682570
According to Robert Vieira, author "SQL Server 7.0 Programming", he seems to lean towards ODBC if you are strictly working with tabular like data (i.e. rows and columns)
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Expert Comment

ID: 2683004
Although SQLOLEDB should be slightly faster, I've found it behaves a bit unpredictable at some points. For instance, when using ADODB.Command objects, the second execution of such a command-object will sometimes clear your parameters (but not all times), even when you've just set them explicitly. I would recommend using one of Marine's first two code-examples.

Expert Comment

ID: 2683091
 The answers given by Marine and others are absolutely correct. But even if you face any problems to make connection to any database Try this simple method out to get the connection string. Place a ADO DataControl on the form and establish the connection using the details given on the property page, when you give the neccessary information like your database name and provider name displayed on the screen. And test the connection you end up with connection string. Copy the string and use it in the code.

Accepted Solution

Jagertee earned 50 total points
ID: 2683505
Easiest is to register your server with Control Panel -> ODBC, give it a unique Data Source Name (DSN), let's say "MyDatabase".

I don't like Data Controls because they're not flexible enough. I'm using the ADO, so you need to reference (Project->References in VB) "Microsoft OLE DB ActiveX Data Object 1.0 Library".

At the start of the application I open the database connection to my server and leave it open till the user closes the app. For this, I use a Public variable in a Module to hold the database connection:

Public DBConn as New ADODB.Connection

Here's the code to open a database connection to your server:

DBConn.Open "MyDatabase", "UserName", "Password"

Somewhere deeper in the code you would like to fetch some records from the database... do it this way to be completely sure that it's working:

On Error Resume Next

Dim RS As ADODB.Recordset
Dim EOF As Boolean

Set RS = DBConn.Execute("SELECT * FROM addresses WHERE city='London'")

If Err = 0 Then
    If EOF Then
        MsgBox "Nothing found!"
        While (Not EOF) And (Err = 0)
            'display current record (just the person's name)
            Debug.Print RS.Fields("name")

            'move to next record
            Err = 0
            EOF = RS.EOF
    End If
End If
If Err Then
    MsgBox "There's been an error in the query: " & Err & " (" & Error & ")"
End If

Need more?

Author Comment

ID: 2686164

Do I have to specify DNS name in the connection command?

Please give me more examples...


Expert Comment

ID: 2686445
You may also use Marine's connection string if you prefer to not register a System DSN in the ODBC control panel applet:

"DRIVER=SQL SERVER;SERVER=yourserver;UID=yourusername;PWD=yourpassword;DATABASE=yourdatabase"

(this is usefull if you have to deploy lots of clients)

for yourserver you may use
- ip address
- netbios name
- dns name (if you have dns deployed in your company or if your server is on the internet)
- dns name (a *must* in a native windows 2000 network)

yourusername and yourpassword should be a valid login for the server and yourdatabase

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