Provided by Allen Browne, June 2008.
You have set up a one-to-many relationship, and now you want a query to show the records from the table on the ONE side, with the items from the MANY side beside each one. For example if one company has many orders, and you want to list the order dates like this:
|Acme Corporation||1/1/2007, 3/1/2007, 7/1/2000, 1/1/2008|
|Wright Time Pty Ltd||4/4/2007, 9/9/2007|
JET SQL does not provide an easy way to do this. A VBA function call is the simplest solution.
Add the function to your database:
You can then use it just like any of the built-in functions, e.g. in a calculated query field, in the ControlSource of a text box on a form or report, in a macro or in other code.
For the example above, you could set the ControlSource of a text box to:
=ConcatRelated("OrderDate", "tblOrders", "CompanyID = " & [CompanyID])
or in a query:
Bug warning: If the function returns more than 255 characters, and you use it in a query as the source for another recordset, a bug in Access may return garbage for the remaining characters.
Inside the brackets for ConcatRelated(), place this information:
Public Function ConcatRelated(strField As String, _ strTable As String, _ Optional strWhere As String, _ Optional strOrderBy As String, _ Optional strSeparator = ", ") As Variant On Error GoTo Err_Handler 'Purpose: Generate a concatenated string of related records. 'Return: String variant, or Null if no matches. 'Arguments: strField = name of field to get results from and concatenate. ' strTable = name of a table or query. ' strWhere = WHERE clause to choose the right values. ' strOrderBy = ORDER BY clause, for sorting the values. ' strSeparator = characters to use between the concatenated values. 'Notes: 1. Use square brackets around field/table names with spaces or odd characters. ' 2. strField can be a Multi-valued field (A2007 and later), but strOrderBy cannot. ' 3. Nulls are omitted, zero-length strings (ZLSs) are returned as ZLSs. ' 4. Returning more than 255 characters to a recordset triggers this Access bug: ' http://allenbrowne.com/bug-16.html Dim rs As DAO.Recordset 'Related records Dim rsMV As DAO.Recordset 'Multi-valued field recordset Dim strSql As String 'SQL statement Dim strOut As String 'Output string to concatenate to. Dim lngLen As Long 'Length of string. Dim bIsMultiValue As Boolean 'Flag if strField is a multi-valued field. 'Initialize to Null ConcatRelated = Null 'Build SQL string, and get the records. strSql = "SELECT " & strField & " FROM " & strTable If strWhere <> vbNullString Then strSql = strSql & " WHERE " & strWhere End If If strOrderBy <> vbNullString Then strSql = strSql & " ORDER BY " & strOrderBy End If Set rs = DBEngine(0)(0).OpenRecordset(strSql, dbOpenDynaset) 'Determine if the requested field is multi-valued (Type is above 100.) bIsMultiValue = (rs(0).Type > 100) 'Loop through the matching records Do While Not rs.EOF If bIsMultiValue Then 'For multi-valued field, loop through the values Set rsMV = rs(0).Value Do While Not rsMV.EOF If Not IsNull(rsMV(0)) Then strOut = strOut & rsMV(0) & strSeparator End If rsMV.MoveNext Loop Set rsMV = Nothing ElseIf Not IsNull(rs(0)) Then strOut = strOut & rs(0) & strSeparator End If rs.MoveNext Loop rs.Close 'Return the string without the trailing separator. lngLen = Len(strOut) - Len(strSeparator) If lngLen > 0 Then ConcatRelated = Left(strOut, lngLen) End If Exit_Handler: 'Clean up Set rsMV = Nothing Set rs = Nothing Exit Function Err_Handler: MsgBox "Error " & Err.Number & ": " & Err.Description, vbExclamation, "ConcatRelated()" Resume Exit_Handler End Function
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