CreateRelation Method Example

This example uses the CreateRelation method to create a Relation between the Employees TableDef and a new TableDef called Departments. This example also demonstrates how creating a new Relation will also create any necessary Indexes in the foreign table (the DepartmentsEmployees Index in the Employees table).

Sub CreateRelationX()

    Dim dbsNorthwind As Database
    Dim tdfEmployees As TableDef
    Dim tdfNew As TableDef
    Dim idxNew As Index
    Dim relNew As Relation
    Dim idxLoop As Index

    Set dbsNorthwind = OpenDatabase("Northwind.mdb")

    With dbsNorthwind
        ' Add new field to Employees table.
        Set tdfEmployees = .TableDefs!Employees
        tdfEmployees.Fields.Append _
            tdfEmployees.CreateField("DeptID", dbInteger, 2)

        ' Create new Departments table.
        Set tdfNew = .CreateTableDef("Departments")

        With tdfNew
            ' Create and append Field objects to Fields
            ' collection of the new TableDef object.
            .Fields.Append .CreateField("DeptID", dbInteger, 2)
            .Fields.Append .CreateField("DeptName", dbText, 20)

            ' Create Index object for Departments table.
            Set idxNew = .CreateIndex("DeptIDIndex")
            ' Create and append Field object to Fields 
            ' collection of the new Index object.
            idxNew.Fields.Append idxNew.CreateField("DeptID")
            ' The index in the primary table must be Unique in
            ' order to be part of a Relation.
            idxNew.Unique = True
            .Indexes.Append idxNew
        End With

        .TableDefs.Append tdfNew

        ' Create EmployeesDepartments Relation object, using 
        ' the names of the two tables in the relation.
        Set relNew = .CreateRelation("EmployeesDepartments", _
            tdfNew.Name, tdfEmployees.Name, _
            dbRelationUpdateCascade)

        ' Create Field object for the Fields collection of the 
        ' new Relation object. Set the Name and ForeignName 
        ' properties based on the fields to be used for the 
        ' relation.
        relNew.Fields.Append relNew.CreateField("DeptID")
        relNew.Fields!DeptID.ForeignName = "DeptID"
        .Relations.Append relNew

        ' Print report.
        Debug.Print "Properties of " & relNew.Name & _
            " Relation"
        Debug.Print "  Table = " & relNew.Table
        Debug.Print "  ForeignTable = " & _
            relNew.ForeignTable
        Debug.Print "Fields of " & relNew.Name & " Relation"

        With relNew.Fields!DeptID
            Debug.Print "  " & .Name
            Debug.Print "    Name = " & .Name
            Debug.Print "    ForeignName = " & .ForeignName
        End With

        Debug.Print "Indexes in " & tdfEmployees.Name & _
            " TableDef"
        For Each idxLoop In tdfEmployees.Indexes
            Debug.Print "  " & idxLoop.Name & _
                ", Foreign = " & idxLoop.Foreign
        Next idxLoop

        ' Delete new objects because this is a demonstration.
        .Relations.Delete relNew.Name
        .TableDefs.Delete tdfNew.Name
        tdfEmployees.Fields.Delete "DeptID"
        .Close
    End With

End Sub