Importing/Exporting Relationships

Question

I have a couple of mdb files with the exact table structure. I have to change the primary key of the main table from autonumber to number in all of them, which means I have

Answer 1

Based on @Patrick Cuff's answer, I have created a pair of scripts: one exporting into xml, other reading this xml and parsing it into the database

VBScript for exporting relationships from MsAccess into XML

'supply the Access Application object into this function and path to file to which the output should be written
Function ExportRelationships(oApplication, sExportpath)
 Dim relDoc, myObj
 Set relDoc = CreateObject("Microsoft.XMLDOM")
 relDoc.appendChild relDoc.createElement("Relations") 'create root xml element

 'loop though all the relations
 For Each myObj In oApplication.CurrentDb.Relations
  If Not Left(myObj.Name, 4) = "MSys" Then 'exclude system relations
   Dim relName, relAttrib, relTable, relFoTable, fld

   relDoc.childNodes(0).appendChild relDoc.createElement("Relation")

   Set relName = relDoc.createElement("Name")
   relName.Text = myObj.Name
   relDoc.childNodes(0).lastChild.appendChild relName

   Set relAttrib = relDoc.createElement("Attributes")
   relAttrib.Text = myObj.Attributes
   relDoc.childNodes(0).lastChild.appendChild relAttrib

   Set relTable = relDoc.createElement("Table")
   relTable.Text = myObj.Table
   relDoc.childNodes(0).lastChild.appendChild relTable

   Set relFoTable = relDoc.createElement("ForeignTable")
   relFoTable.Text = myObj.ForeignTable
   relDoc.childNodes(0).lastChild.appendChild relFoTable

   'in case the relationship works with more fields
   For Each fld In myObj.Fields
    Dim lf, ff
    relDoc.childNodes(0).lastChild.appendChild relDoc.createElement("Field")

    Set lf = relDoc.createElement("Name")
    lf.Text = fld.Name
    relDoc.childNodes(0).lastChild.lastChild.appendChild lf

    Set ff = relDoc.createElement("ForeignName")
    ff.Text = fld.ForeignName
    relDoc.childNodes(0).lastChild.lastChild.appendChild ff
   Next
  End If
 Next
 relDoc.insertBefore relDoc.createProcessingInstruction("xml","version='1.0'"), relDoc.childNodes(0)
 relDoc.Save sExportpath
End Function

VBScript for importing relationships into MsAccess from XML

'supply the Access Application object into this function and path to file from which the input should be read
Function ImportRelationships(oApplication, sImportpath)
 Dim relDoc, myObj
 Set relDoc = CreateObject("Microsoft.XMLDOM")
 relDoc.Load(sImportpath)
 Dim xmlRel, xmlField, accessRel, relTable, relName, relFTable, relAttr, i

 'loop through every Relation node inside .xml file
 For Each xmlRel in relDoc.selectNodes("/Relations/Relation")
  relName = xmlRel.selectSingleNode("Name").Text
  relTable = xmlRel.selectSingleNode("Table").Text
  relFTable = xmlRel.selectSingleNode("ForeignTable").Text
  relAttr = xmlRel.selectSingleNode("Attributes").Text

  'remove any possible conflicting relations or indexes
  On Error Resume next
  oApplication.CurrentDb.Relations.Delete (relName)
  oApplication.CurrentDb.TableDefs(relTable).Indexes.Delete(relName)
  oApplication.CurrentDb.TableDefs(relFTable).Indexes.Delete(relName)
  On Error Goto 0

  'create the relationship object
  Set accessRel = oApplication.CurrentDb.CreateRelation(relName, relTable, relFTable, relAttr)

  'in case the relationship works with more fields
  For Each xmlField In xmlRel.selectNodes("Field")
   accessRel.Fields.Append accessRel.CreateField(xmlField.selectSingleNode("Name").Text)
   accessRel.Fields(xmlField.selectSingleNode("Name").Text).ForeignName = xmlField.selectSingleNode("ForeignName").Text
  Next

  'and finally append the newly created relationship to the database
  oApplication.CurrentDb.Relations.Append accessRel
 Next
End Function

Notes

Just to clarify what is expected to be passed into oApplication parameter

Set oApplication = CreateObject("Access.Application")
oApplication.NewCurrentDatabase path   'new database
oApplication.OpenCurrentDatabase path  'existing database

In case you are running this from VBA instead of VBScript, you can delete the parameter and just the regular Application object everywhere in the code where oApplication is being used.

---

I got started to work on this code as I needed to implement a Version Control on a very complicated MsAccess project. This post got me moving, there are also some good advices on how to export/import other parts of the MsAccess project.

Answer 2

It occurs to me that you can use a backup of the file made before any changes to restore the indexes and relations. Here are some notes.

Sub RunExamples()
Dim strCopyMDB As String
Dim fs As FileSystemObject
Dim blnFound As Boolean
Dim i

' This code is not intended for general users, it is sample code built '
' around the OP '
'You will need a reference to the Microsoft DAO 3.x Object Library '
'This line causes an error, but it will run '
'It is not suitable for anything other than saving a little time '
'when setting up a new database '
Application.References.AddFromFile ("C:\Program Files\Common Files\Microsoft Shared\DAO\dao360.dll")

'You must first create a back-up copy '
Set fs = CreateObject("Scripting.FileSystemObject")

strCopyMDB = CurrentProject.Path & "\c.mdb"
blnFound = fs.FileExists(strCopyMDB)

i = 0
Do While blnFound
    strCopyMDB = CurrentProject.Path & "\c" & i & ".mdb"
    blnFound = fs.FileExists(strCopyMDB)
Loop

fs.CopyFile CurrentProject.FullName, strCopyMDB

ChangeTables
AddIndexesFromBU strCopyMDB
AddRelationsFromBU strCopyMDB
End Sub  


Sub ChangeTables()
Dim db As Database
Dim tdf As DAO.TableDef
Dim rel As DAO.Relation
Dim fld As DAO.Field
Dim ndx As DAO.Index
Dim i

    Set db = CurrentDb
    'In order to programmatically change an autonumber, '
    'it is necessary to delete any relationships that '
    'depend on it. '  
    'When deleting from a collection, it is best '
    'to iterate backwards. '
    For i = db.Relations.Count - 1 To 0 Step -1
        db.Relations.Delete db.Relations(i).Name
    Next

    'The indexes must also be deleted or the '
    'number cannot be changed. '
    For Each tdf In db.TableDefs
        If Left(tdf.Name, 4) <> "Msys" Then
            For i = tdf.Indexes.Count - 1 To 0 Step -1
                tdf.Indexes.Delete tdf.Indexes(i).Name
            Next

            tdf.Indexes.Refresh

            For Each fld In tdf.Fields
                'If the field is an autonumber, '
                'use code supplied by MS to change the type '
                If (fld.Attributes And dbAutoIncrField) Then

                    AlterFieldType tdf.Name, fld.Name, "Long"

                End If
            Next
        End If

    Next
End Sub


Sub AddIndexesFromBU(MDBBU)
Dim db As Database
Dim dbBU As Database
Dim tdf As DAO.TableDef
Dim tdfBU As DAO.TableDef
Dim ndx As DAO.Index
Dim ndxBU As DAO.Index
Dim i

Set db = CurrentDb
'This is the back-up made before starting '
Set dbBU = OpenDatabase(MDBBU)

    For Each tdfBU In dbBU.TableDefs
        'Skip system tables '
        If Left(tdfBU.Name, 4) <> "Msys" Then
            For i = tdfBU.Indexes.Count - 1 To 0 Step -1
                'Get each index from the back-up '
                Set ndxBU = tdfBU.Indexes(i)
                Set tdf = db.TableDefs(tdfBU.Name)
                Set ndx = tdf.CreateIndex(ndxBU.Name)
                ndx.Fields = ndxBU.Fields
                ndx.IgnoreNulls = ndxBU.IgnoreNulls
                ndx.Primary = ndxBU.Primary
                ndx.Required = ndxBU.Required
                ndx.Unique = ndxBU.Unique

                ' and add it to the current db '
                tdf.Indexes.Append ndx
            Next

            tdf.Indexes.Refresh
        End If
    Next

End Sub

Sub AddRelationsFromBU(MDBBU)
Dim db As Database
Dim dbBU As Database
Dim rel As DAO.Relation
Dim fld As DAO.Field
Dim relBU As DAO.Relation
Dim i, j, f

On Error GoTo ErrTrap

    Set db = CurrentDb
    'The back-up again '
    Set dbBU = OpenDatabase(MDBBU)

    For i = dbBU.Relations.Count - 1 To 0 Step -1
        'Get each relationship from bu '
        Set relBU = dbBU.Relations(i)
        Debug.Print relBU.Name
        Set rel = db.CreateRelation(relBU.Name, relBU.Table, relBU.ForeignTable, relBU.Attributes)
        For j = 0 To relBU.Fields.Count - 1
            f = relBU.Fields(j).Name
            rel.Fields.Append rel.CreateField(f)
            rel.Fields(f).ForeignName = relBU.Fields(j).ForeignName
        Next
        'For some relationships, I am getting error'
        '3284 Index already exists, which I will try'
        'and track down tomorrow, I hope'
        'EDIT: Apparently this is due to Access creating hidden indexes
        'and tracking these down would take quite a bit of effort
        'more information can be found in this link:
        'http://groups.google.ie/group/microsoft.public.access/browse_thread/thread/ca58ce291bdc62df?hl=en&ie=UTF-8&q=create+relation+3284+Index+already+exists
        'It is an occasional problem, so I've added an error trap

         'Add the relationship to the current db'
         db.Relations.Append rel
    Next
ExitHere:
    Exit Sub

ErrTrap:
    If Err.Number = 3284 Then
        Debug.Print relBU.Name, relBU.Table, relBU.ForeignTable, relBU.Attributes
        Resume Next
    Else
        'this is not a user sub, so may as well ... '
        Stop

End If
End Sub

Sub AlterFieldType(TblName As String, FieldName As String, _
    NewDataType As String)
'http://support.microsoft.com/kb/128016'

    Dim db As Database
    Dim qdf As QueryDef
    Set db = CurrentDb()

    ' Create a dummy QueryDef object.'
    Set qdf = db.CreateQueryDef("", "Select * from PROD1")

    ' Add a temporary field to the table.'
    qdf.SQL = "ALTER TABLE [" & TblName & "] ADD COLUMN AlterTempField " & NewDataType
    qdf.Execute

    ' Copy the data from old field into the new field.'
    qdf.SQL = "UPDATE DISTINCTROW [" & TblName _
        & "] SET AlterTempField = [" & FieldName & "]"
    qdf.Execute

    ' Delete the old field.'
    qdf.SQL = "ALTER TABLE [" & TblName & "] DROP COLUMN [" _
       & FieldName & "]"
    qdf.Execute

    ' Rename the temporary field to the old field's name.'
    db.TableDefs("[" & TblName & "]").Fields("AlterTempField").Name = FieldName

End Sub

Answer 3

Not a complete solution, but this may get you going...

The following function will print out the metadata for all relationships. Change this to save to a file in whatever format you prefer (CSV, tab delimited, XML, etc.):

Function PrintRelationships()
    For Each rel In CurrentDb.Relations
        With rel
            Debug.Print "Name: " & .Name
            Debug.Print "Attributes: " & .Attributes
            Debug.Print "Table: " & .Table
            Debug.Print "ForeignTable: " & .ForeignTable

            Debug.Print "Fields:"
            For Each fld In .Fields
                Debug.Print "Field: " & fld.Name
            Next
        End With
    Next
End Function

This function will drop all the relationships in the database:

Function DropRelationships()
    With CurrentDb
        For Each rel In .Relations
            .Relations.Delete Name:=rel.Name
        Next
    End With
End Function

This function will create a relationship. You'll have to iterate over the file of saved relationship data.

Function CreateRelationships()
    With CurrentDb
        Set rel = .CreateRelation(Name:="[rel.Name]", Table:="[rel.Table]", ForeignTable:="[rel.FireignTable]", Attributes:=[rel.Attributes])
        rel.Fields.Append rel.CreateField("[fld.Name for relation]")
        rel.Fields("[fld.Name for relation]").ForeignName = "[fld.Name for relation]"
        .Relations.Append rel
    End With
End Function

Error handling and IO omitted due to time constraints (gotta put the kids to bed).

Hope this helps.

Answer 4

Thanks for code snippet. to get rid of your 3284 error I have changed a few things. If you copy all indexes from sample mdb and then try to put relationships it throws an exception as it expects no idexes for relationshisps when you put relationships it puts its own indexes. Steps I followed are (assume target.mdb and source.mdb):

1. Run this code in target.mdb remove all indexes and relationsships frmo target.mdb by calling ChangeTables
2. Call AddIndexesFromBU source.mdb and use condition
   If ndxBU.Unique Then tdf.Indexes.Append ndx End If this willput just Unique index
3. call AddRelationsFromBU source.mdb and put all relationsships
4. Call again AddIndexesFromBU source.mdb and change condition to If not ndxBU.Unique Then

I have also added error trap same as AddRelationsFromBU in AddIndexesFromBU and resume next for if ans else

This worked for me.