Using ADO in VBA to connect to PostgreSQL

问题

I am having trouble finding clear and reliable examples of connecting to a PostgreSQL database from Excel using VBA ADO. Admittedly, I am new to VBA and most examples and tutorials are very Access or MSSQL centered. (I work mostly in Ruby, Rails, Perl and PostgreSQL.)

I am looking for code to connect and return a simple query (SELECT * FROM customers;) to an Excel sheet. Connection parameters (server ip, user, pass, database) are located within cells in a separate worksheet.

I appreciate your help and patience.

Code:

Sub ConnectDatabaseTest()
Dim cnn As ADODB.connection
Dim cmd As ADODB.Command
Dim param As ADODB.Parameter
Dim xlSheet As Worksheet
Dim rs As ADODB.Recordset
Dim sConnString As String
Dim i As Integer

' Connection Parameters
Dim strUsername As String
Dim strPassword As String
Dim strServerAddress As String
Dim strDatabase As String
' User:
strUsername = Sheets("CONFIG").Range("B4").Value
' Password:
strPassword = Sheets("CONFIG").Range("B5").Value
' Server Address:
strServerAddress = Sheets("CONFIG").Range("B6").Value
' Database
strDatabase = Sheets("CONFIG").Range("B3").Value

Set xlSheet = Sheets("TEST")
xlSheet.Activate
Range("A3").Activate
Selection.CurrentRegion.Select
Selection.ClearContents
Range("A1").Select

Set cnn = New ADODB.connection
sConnString = "DRIVER={PostgreSQL Unicode};DATABASE=" & strDatabase & ";SERVER=" & strServerAddress & _
    ";UID=" & strUsername & ";PWD=" & strPassword
cnn.Open sConnString

cmd.ActiveConnection = cnn

Dim strSQL As String
strSQL = "SELECT * FROM customers"

cmd.CommandType = ADODB.CommandTypeEnum.adCmdText
cmd.ActiveConnection = cnn
cmd.CommandText = strSQL
...

It seems to break here: cmd.ActiveConnection = cnn

EDIT: added sample code.

EDIT: sConnString gets set to:

DRIVER={PostgreSQL35W};DATABASE=my_database;SERVER=1.2.3.4;UID=analyst;PWD=sekrit

UPDATE 2/7: I changed the 'DRIVER' parameter in the connection string:

    sConnString = "DRIVER={PostgreSQL Unicode};DATABASE=" & strDatabase & ";SERVER=" & strServerAddress & _
    ";UID=" & strUsername & ";PWD=" & strPassword & ";"

...and I get a different error: 'Run-time error 91: Object variable or With block variable not set'

Hm. Ideas?

回答1:

I wan't using a DSN as I am using an ODBC driver as opposed to OLE DB. By referencing a DSN, the above code works with very few changes.

See this question for how I found the answer once I began to suspect OLE DB/ODBC to the issue. Does ADO work with ODBC drivers or only OLE DB providers?

New Code here:

Sub GetCustomers()
Dim oConn As New ADODB.connection
Dim cmd As New ADODB.Command
' Connection Parameters
Dim strUsername As String
Dim strPassword As String
Dim strServerAddress As String
Dim strDatabase As String
' User:
strUsername = Sheets("CONFIG").Range("B4").Value
' Password:
strPassword = Sheets("CONFIG").Range("B5").Value
' Server Address:
strServerAddress = Sheets("CONFIG").Range("B6").Value
' Database
strDatabase = Sheets("CONFIG").Range("B3").Value


oConn.Open "DSN=my_system_dsn;" & _
    "Database=" & strDatabase & ";" & _
    "Uid=" & strUsername & ";" & _
    "Pwd=" & strPassword

Set xlSheet = Sheets("CUSTOMERS")
xlSheet.Activate
Range("A3").Activate
Selection.CurrentRegion.Select
Selection.ClearContents
Range("A1").Select

Dim strSQL As String
strSQL = "SELECT * FROM customers"

cmd.CommandType = ADODB.CommandTypeEnum.adCmdText
cmd.ActiveConnection = oConn
cmd.CommandText = strSQL

Set rs = New ADODB.Recordset
Set rs = cmd.Execute

For i = 1 To rs.Fields.Count
    ActiveSheet.Cells(3, i).Value = rs.Fields(i - 1).Name
Next i

xlSheet.Range(xlSheet.Cells(3, 1), _
    xlSheet.Cells(3, rs.Fields.Count)).Font.Bold = True

ActiveSheet.Range("A4").CopyFromRecordset rs

xlSheet.Select
Range("A3").Select
Selection.CurrentRegion.Select
Selection.Columns.AutoFit
Range("A1").Select

rs.Close
oConn.Close

Set cmd = Nothing
Set param = Nothing
Set rs = Nothing
Set cnn = Nothing
Set xlSheet = Nothing
End Sub

The System DSN is configured to use the PostgreSQL Unicode driver. I chose not to use OLE DB even though there is a provider available. If you look at PGFoundry, you will see it has many problems and has not been updated in several years.

回答2:

In the original Code, "PostgreSQL35W" is a DSN name which included the default host and port. When you changed to "PostgreSQL Unicode", it is a driver and your connection string is lacking the value for the port. Remember to access PostgreSQL directly from driver, you need at least 5 parameters:

• host
• port
• userid
• password
• database

If you are using DSN, some parameters may be defined as default.

回答3:

Not sure about the details of the actual DB connection, but there is a simple although common mistake with your statement: you need to use 'set' when working with objects:

set cmd.ActiveConnection = cnn

来源：https://stackoverflow.com/questions/9117516/using-ado-in-vba-to-connect-to-postgresql