Database.CreateRelation method (DAO)

Applies to: Access 2013, Office 2013

Creates a new Relation object (Microsoft Access workspaces only). .

Syntax

expression .CreateRelation(Name, Table, ForeignTable, Attributes)

expression A variable that represents a Database object.

Parameters

Name	Required/optional	Data type	Description
Name	Optional	Variant	A Variant (String subtype) that uniquely names the new Relation object. See the Name property for details on valid Relation names.
Table	Optional	Variant	A Variant (String subtype) that names the primary table in the relation. If the table doesn't exist before you append the Relation object, a run-time error occurs.
ForeignTable	Optional	Variant	A Variant (String subtype) that names the foreign table in the relation. If the table doesn't exist before you append the Relation object, a run-time error occurs.
Attributes	Optional	Variant	A constant or combination of constants that contains information about the relationship type. See the Attributes property for details.

Return value

Relation

Remarks

The Relation object provides information to the Microsoft Access database engine about the relationship between fields in two TableDef or QueryDef objects. You can implement referential integrity by using the Attributes property.

If you omit one or more of the optional parts when you use the CreateRelation method, you can use an appropriate assignment statement to set or reset the corresponding property before you append the new object to a collection. After you append the object, you can't alter any of its property settings. See the individual property topics for more details.

Before you can use the Append method on a Relation object, you must append the appropriate Field objects to define the primary and foreign key relationship tables.

If name refers to an object that is already a member of the collection or if the Field object names provided in the subordinate Fields collection are invalid, a run-time error occurs when you use the Append method.

You can't establish or maintain a relationship between a replicated table and a local table.

To remove a Relation object from the Relations collection, use the Delete method on the collection.

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