Access里自定义类似MySQL group_concat 的函数

Concatenate fields in same table
Author(s)
Dev Ashish

(Q)    I need to concatenate a field in the format "Value1; Value2; Value3" etc. for each unique value of another field in the same table.  How can I do this?

(A)    Using the fConcatFld function,  in the Northwind database, the following query should return a concatenated list of all CustomerIDs if you group by ContactTitle.

SELECT ContactTitle, fConcatFld("Customers","ContactTitle","CustomerID","string",[ContactTitle]) AS Customers FROM Customers GROUP BY ContactTitle;

'************ Code Start **********
'This code was originally written by Dev Ashish
'It is not to be altered or distributed,
'except as part of an application.
'You are free to use it in any application,
'provided the copyright notice is left unchanged.
'
'Code Courtesy of
'Dev Ashish
'
Function fConcatFld(stTable As String, _
stForFld As String, _
stFldToConcat As String, _
stForFldType As String, _
vForFldVal As Variant) _
As String
'Returns mutiple field values for each unique value
'of another field in a single table
'in a semi-colon separated format.
'
'Usage Examples:
'   ?fConcatFld(("Customers","ContactTitle","CustomerID", _
'                "string","Owner")
'Where  Customers     = The parent Table
'       ContactTitle  = The field whose values to use for lookups
'       CustomerID    = Field name to concatenate
'       string        = DataType of ContactTitle field
'       Owner         = Value on which to return concatenated CustomerID
'
Dim lodb As Database, lors As Recordset
Dim lovConcat As Variant, loCriteria As String
Dim loSQL As String
Const cQ = """"

On Error GoTo Err_fConcatFld

lovConcat = Null
Set lodb = CurrentDb

loSQL = "SELECT [" & stFldToConcat & "] FROM ["
loSQL = loSQL & stTable & "] WHERE "

Select Case stForFldType
Case "String":
loSQL = loSQL & "[" & stForFld & "] =" & cQ & vForFldVal & cQ
Case "Long", "Integer", "Double":    'AutoNumber is Type Long
loSQL = loSQL & "[" & stForFld & "] = " & vForFldVal
Case Else
GoTo Err_fConcatFld
End Select

Set lors = lodb.OpenRecordset(loSQL, dbOpenSnapshot)

'Are we sure that duplicates exist in stFldToConcat
With lors
If .RecordCount <> 0 Then
'start concatenating records
Do While Not .EOF
lovConcat = lovConcat & lors(stFldToConcat) & "; "
.MoveNext
Loop
Else
GoTo Exit_fConcatFld
End If
End With

'That's it... you should have a concatenated string now
'Just Trim the trailing ;
fConcatFld = Left(lovConcat, Len(lovConcat) - 2)

Exit_fConcatFld:
Set lors = Nothing: Set lodb = Nothing
Exit Function

Err_fConcatFld:
MsgBox "Error#: " & Err.Number & vbCrLf & Err.Description
Resume Exit_fConcatFld
End Function
'************ Code End **********