TableDef Object (DAO)

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10/12/2015

A TableDef object represents the stored definition of a base table or a linked table (Microsoft Access workspaces only).

Remarks

You manipulate a table definition using a TableDef object and its methods and properties. For example, you can:

Examine the field and index structure of any local, linked, or external table in a database.
Use the Connect and SourceTableName properties to set or return information about linked tables, and use the RefreshLink method to update connections to linked tables.
Use the ValidationRule and ValidationText properties to set or return validation conditions.
Use the OpenRecordset method to create a table–, dynaset–, dynamic–, snapshot–, or forward–only–type Recordset object, based on the table definition.

For base tables, the RecordCount property contains the number of records in the specified database table. For linked tables, the RecordCount property setting is always –1.

To create a new TableDef object, use the CreateTableDef method.

To add a field to a table

Make sure any Recordset objects based on the table are all closed.
Use the CreateField method to create a Field object variable and set its properties.
Use the Append method to add the Field object to the Fields collection of the TableDef object.

You can delete a Field object from a TableDefs collection if it doesn't have any indexes assigned to it, but you will lose the field's data.

To create a table that is ready for new records in a database

Use the CreateTableDef method to create a TableDef object.
Set its properties.
For each field in the table, use the CreateField method to create a Field object variable and set its properties.
Use the Append method to add the fields to the Fields collection of the TableDef object.
Use the Append method to add the new TableDef object to the TableDefs collection of the Database object.

A linked table is connected to the database by the SourceTableName and Connect properties of the TableDef object.

To link a table to a database

Use the CreateTableDef method to create a TableDef object.
Set its Connect and SourceTableName properties (and optionally, its Attributes property).
Use the Append method to add it to the TableDefs collection of a Database.

To refer to a TableDef object in a collection by its ordinal number or by its Name property setting, use any of the following syntax forms:

TableDefs(0)

TableDefs("name")

TableDefs![name]

Example

This example creates a new TableDef object and appends it to the TableDefs collection of the Northwind Database object. It then enumerates the TableDefs collection and the Properties collection of the new TableDef.

Sub TableDefX() 
 
   Dim dbsNorthwind As Database 
   Dim tdfNew As TableDef 
   Dim tdfLoop As TableDef 
   Dim prpLoop As Property 
 
   Set dbsNorthwind = OpenDatabase("Northwind.mdb") 
 
   ' Create new TableDef object, append Field objects  
   ' to its Fields collection, and append TableDef  
   ' object to the TableDefs collection of the  
   ' Database object. 
   Set tdfNew = dbsNorthwind.CreateTableDef("NewTableDef") 
   tdfNew.Fields.Append tdfNew.CreateField("Date", dbDate) 
   dbsNorthwind.TableDefs.Append tdfNew 
 
   With dbsNorthwind 
      Debug.Print .TableDefs.Count & _ 
         " TableDefs in " & .Name 
 
      ' Enumerate TableDefs collection. 
      For Each tdfLoop In .TableDefs 
         Debug.Print "  " & tdfLoop.Name 
      Next tdfLoop 
 
      With tdfNew 
         Debug.Print "Properties of " & .Name 
 
         ' Enumerate Properties collection of new 
         ' TableDef object, only printing properties 
         ' with non-empty values. 
         For Each prpLoop In .Properties 
            Debug.Print "  " & prpLoop.Name & " - " & _ 
               IIf(prpLoop = "", "[empty]", prpLoop) 
         Next prpLoop 
 
      End With 
 
      ' Delete new TableDef since this is a  
      ' demonstration. 
      .TableDefs.Delete tdfNew.Name 
      .Close 
   End With 
 
End Sub

This example creates a new TableDef object in the Northwind database.

Sub CreateTableDefX() 
 
   Dim dbsNorthwind As Database 
   Dim tdfNew As TableDef 
   Dim prpLoop As Property 
 
   Set dbsNorthwind = OpenDatabase("Northwind.mdb") 
 
   ' Create a new TableDef object. 
   Set tdfNew = dbsNorthwind.CreateTableDef("Contacts") 
 
   With tdfNew 
      ' Create fields and append them to the new TableDef  
      ' object. This must be done before appending the  
      ' TableDef object to the TableDefs collection of the  
      ' Northwind database. 
      .Fields.Append .CreateField("FirstName", dbText) 
      .Fields.Append .CreateField("LastName", dbText) 
      .Fields.Append .CreateField("Phone", dbText) 
      .Fields.Append .CreateField("Notes", dbMemo) 
 
      Debug.Print "Properties of new TableDef object " & _ 
         "before appending to collection:" 
 
      ' Enumerate Properties collection of new TableDef  
      ' object. 
      For Each prpLoop In .Properties 
         On Error Resume Next 
         If prpLoop <> "" Then Debug.Print "  " & _ 
           prpLoop.Name & " = " & prpLoop 
         On Error GoTo 0 
      Next prpLoop 
 
      ' Append the new TableDef object to the Northwind  
      ' database. 
      dbsNorthwind.TableDefs.Append tdfNew 
 
      Debug.Print "Properties of new TableDef object " & _ 
         "after appending to collection:" 
 
      ' Enumerate Properties collection of new TableDef  
      ' object. 
      For Each prpLoop In .Properties 
         On Error Resume Next 
         If prpLoop <> "" Then Debug.Print "  " & _ 
           prpLoop.Name & " = " & prpLoop 
         On Error GoTo 0 
      Next prpLoop 
 
   End With 
 
   ' Delete new TableDef object since this is a  
   ' demonstration. 
   dbsNorthwind.TableDefs.Delete "Contacts" 
 
   dbsNorthwind.Close

The following example shows how to create a calculated field. The CreateField method creates a field named FullName. The Expression property is then set to the expression that calculates the value of the field.

Sample code provided by: Access 2010 Programmers Reference book cover The Microsoft Access 2010 Programmer’s Reference | About the Contributors

Sub CreateCalculatedField()
    Dim dbs As DAO.Database
    Dim tdf As DAO.TableDef
    Dim fld As DAO.Field2
    
    ' get the database
    Set dbs = CurrentDb()
    
    ' create the table
    Set tdf = dbs.CreateTableDef("tblContactsCalcField")
    
    ' create the fields: first name, last name
    tdf.Fields.Append tdf.CreateField("FirstName", dbText, 20)
    tdf.Fields.Append tdf.CreateField("LastName", dbText, 20)
    
    ' create the calculated field: full name
    Set fld = tdf.CreateField("FullName", dbText, 50)
    fld.Expression = "[FirstName] & "" "" & [LastName]"
    tdf.Fields.Append fld
    
    ' append the table and cleanup
    dbs.TableDefs.Append tdf
    
Cleanup:
    Set fld = Nothing
    Set tdf = Nothing
    Set dbs = Nothing
End Sub

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