Microsoft Knowledge Base Article
This article contents is Microsoft Copyrighted material.
©2005-©2007 Microsoft Corporation. All rights reserved.
Terms
of Use |
Trademarks
How To DAO: Attach to and Create QueryDefs on ODBC Tables
| Article ID | : | 150716 |
| Last Review | : | March 14, 2005 |
| Revision | : | 2.3 |
This article was previously published under Q150716
On This Page
SUMMARY
This article describes how to attach and create Querydefs on external ODBC
tables. The method for opening external ODBC tables is to attach the tables
to an .mdb file.
Jet does not support named QueryDefs on a non-attached ODBC database. A non-
attached ODBC database is one that is opened directly with the OpenDatabase
method of the WorkSpace object without the use of an .mdb file.
If it is not appropriate for the application to attach the ODBC tables, it
is possible to create Querydefs with no name to accomplish the procedure.
For additional information, please see the following article in the
Microsoft Knowledge Base:
149055 (http://kbalertz.com/Feedback.aspx?kbNumber=149055/EN-US/)
: Jet Doesn't Support QueryDefs on a Non-Attached ODBC Table
Back to the top
MORE INFORMATION
The following is information from "Guide To Data Access Objects," Chapter
7, Data Access Choices, that explains this procedure:
In many cases, attaching a table to access external data is faster than
opening a table directly, especially if the data is located in an ODBC
database. In Visual Basic version 4.0, SQL Passthrough is used to query
attached ODBC databases directly. Consider attaching external tables rather
than opening them directly. Using external data in an ODBC database
requires opening the external tables directly so performance is
significantly slower when using the data.
Back to the top
Sample Program
The following example describes how to attach to and create a Querydef on
an ODBC table using a "DSN-less" ODBC connection. With this procedure, it
is not necessary to set up a DSN with the ODBC Admin utility.
| 1. | Start a new project in Visual Basic. Form1 is created by default.
|
| 2. | Add three Command buttons to Form1: Command1, Command2, Command3 by
default.
|
| 3. | Paste the following code in the General Declarations section of Form1:
Dim db As Database
Dim cn As String
Private Sub Form_Load()
cn = "odbc;driver={SQL Server};server=myserver;" & _
"database=pubs;uid=myuid;pwd=mypwd"
If Dir("mydb.mdb") <> "" Then
' database exists, so just open it.
Set db = OpenDatabase(Name:="mydb", Exclusive:=False, _
ReadOnly:=False, Connect:="")
Else
'database does not exist, create it and attach authors table.
Set db = CreateDatabase(Name:="mydb", Connect:=dbLangGeneral, _
Option:=dbVersion30)
Dim td As TableDef
Set td = db.CreateTableDef()
td.Name = "Authors"
td.SourceTableName = "Authors"
td.Connect = cn
End If
End Sub
Private Sub Command1_Click()
Dim qd As QueryDef
On Error Resume Next
Set qd = db.QueryDefs("abc") ' test for existence of querydef.
If Error > 0 Then
Set qd = db.CreateQueryDef(Name:="abc")
qd.Connect = cn
qd.SQL = "Select @@Version" 'native SQL Server
End If
Set qd = db.QueryDefs("xyz") ' test for existence of querydef.
If Error > 0 Then
Set qd = db.CreateQueryDef(Name:="xyz")
qd.Connect = cn
qd.SQL = "Select * from titles" ' generic SQL.
End If
On Error GoTo 0
End Sub
Private Sub Command2_Click()
Dim rs As Recordset
Dim qd As QueryDef
Set qd = db.QueryDefs("abc")
Set rs = qd.OpenRecordset()
Call displayResults(rs)
End Sub
Private Sub Command3_Click()
Dim rs As Recordset
Dim qd As QueryDef
Set qd = db.QueryDefs("xyz")
Set rs = qd.OpenRecordset()
Call displayResults(rs)
End Sub
Sub displayResults(rs As Recordset)
Dim f As Field, s As String, i As Integer
For Each f In rs.Fields
s = s & f.Name
Next f
Debug.Print s ' print column headers.
While Not rs.EOF And i < 5
s = ""
For Each f In rs.Fields
s = s & f.Value
Next f
Debug.Print s ' print first 5 rows.
rs.MoveNext
i = i + 1
Wend
End Sub
|
NOTE: You need to change the DRIVER, SERVER, DATABASE, UID, and PWD
parameters in the OpenConnection method. Also you must modify the SQL
statements contained in the Command1_Click event to match your SQL data
source.
| 1. | Press the F5 key to start the program.
|
| 2. | Click the Command1 button to create the Querydefs. Click the Command2
and Command3 buttons to execute the Querydefs. Note that the first five
rows of data appear in the Debug window.
|
Back to the top
REFERENCES
"Jet Database Engine Programmer's Guide", page 323, published by Microsoft Press.
Back to the top
APPLIES TO
| • | Microsoft Visual Basic 4.0 32-Bit Enterprise Edition |
| • | Microsoft Data Access Components 2.5 |
Back to the top
Community Feedback System
Very often, it takes hours to solve a problem. Very often, you've looked high
and low, and have tried a lot of solutions. When you finally found it, chances
are, it was because someone else helped you. Here's your chance to give back.
Use our community feedback tool to let others know what worked for you and what
didn't.
Please also understand that the community feedback system is not warranted to be
correct, it's simply a system that we've built to let people try and help each
other. If something in a feedback response doesn't make sense to you, or you're
not comfortable making changes that the feedback talks about (like registry
edits), please consult a professional.
Thank you for using kbAlertz.com Feedback System.
-- Scott Cate
Be the first to leave feedback, to help others about this knowledge base
article.
(Optional) Name
(Optional)
Public URL Or Email
Comments
No
HTML -- Text Only Please