TIndexDef.Fields Property

Identifies the fields that comprise the index.

Pascal

property Fields: string;

C++

__property AnsiString Fields;

Description

When creating an index, set Fields to a list of fields separated by semicolons (no semicolon is required if there is only one field in the index). The order of field names in the string determines the order of fields in the index.

When inspecting already-existing indexes, read Fields to determine the fields that make up the index. The string returned can be either the names of the fields, or the numbers of the field. When numbers are used, the numbers correspond to the physical field numbers in the table. Multiple fields in the string are separated by semicolons (;).

Note:

C++ Examples:

Copy Code

/*
The following example shows how to create a table.
*/

void __fastcall TForm1::FormCreate(TObject *Sender)
{
  Table1 = new TTable(Form1);
  Table1->Active = false; // The Table component must not be active
  Table1->DatabaseName = "DBDEMOS";
  Table1->TableType = ttParadox;
  Table1->TableName = "CustInfo";
  if (Table1->Exists)
    MessageDlg("CustInfo table already exists.", mtWarning, TMsgDlgButtons() << mbOK, 0);
  else // Don't overwrite an existing table
  {
    // describe the fields in the table
    Table1->FieldDefs->Clear();
    TFieldDef *newDef = Table1->FieldDefs->AddFieldDef();
    newDef->Name = "Field1";
    newDef->DataType = ftInteger;
    newDef->Required = true;
    newDef = Table1->FieldDefs->AddFieldDef();
    newDef->Name = "Field2";
    newDef->DataType = ftString;
    newDef->Size = 30;
    // Next, describe any indexes
    Table1->IndexDefs->Clear();
    /* the 1st index has no name because it is a Paradox primary key */
    Table1->IndexDefs->Add("","Field1", TIndexOptions() <<ixPrimary << ixUnique);
    Table1->IndexDefs->Add("Fld2Index", "Field2", TIndexOptions() << ixCaseInsensitive);
    // Now that we have specified what we want, create the table
    Table1->CreateTable();
    Table1->Active = True;
    for (int i = 1; i <= 20; i++)
      Table1->AppendRecord(ARRAYOFCONST((i*111, i*222)));
  }
  DS2->DataSet = Table1;
  DBGrid2->DataSource->DataSet = Table1;
  Table1->Active = True;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
  Table1->Close();
  Table1->DeleteTable();
}

Copy Code

/*
This example uses the IndexName property to sort the records
in a client dataset on the Field2 field.
*/
void __fastcall TForm1::Button3Click(TObject *Sender)
{
  // If Active is True, Update will remove Fields added in FormCreate
  // and add the DEFAULT_ORDER and CHANGEINDEX Fields
  CDS2->Active = False;
  // Get the current available indices
  CDS2->IndexDefs->Update();
  // Find a field named "Field2"
  for (int I = 0; I < CDS2->IndexDefs->Count; I++)
    if (CDS2->IndexDefs->Items[I]->Fields == "Field2")
    {
      // set that index as the current index for the dataset}
      CDS2->IndexName = CDS2->IndexDefs->Items[I]->Name;
    }
  CDS2->Active = True;
}

Delphi Examples:

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{ The following example shows how to create a table. }
procedure TForm1.Button1Click(Sender: TObject);
begin
  Table1.Close;
  Table1.DeleteTable;
end;

procedure TForm1.FormCreate(Sender: TObject);
var
  i: Integer;
begin
  Table1:= TTable.Create(Form1);
  with Table1 do
  begin
    DatabaseName := 'DBDEMOS';
    TableType := ttParadox;
    TableName := 'CustInfo';
    Table1.Active := False;
    { Don't overwrite an existing table }
    if Table1.Exists then
      MessageDlg('CustInfo table already exists.', mtWarning, [mbOK], 0)
    else
    begin
      { The Table component must not be active }
      { First, describe the type of table and give }
      { it a name }
      { Next, describe the fields in the table }
      with FieldDefs do
      begin
        Clear;
        with AddFieldDef do
        begin
          Name := 'Field1';
          DataType := ftInteger;
          Required := True;
        end;
        with AddFieldDef do
        begin
          Name := 'Field2';
          DataType := ftString;
          Size := 30;
        end;
      end;
      { Next, describe any indexes }
      with IndexDefs do
      begin
        Clear;
        { The 1st index has no name because it is
        { a Paradox primary key }
        with AddIndexDef do
        begin
          Name := '';
          Fields := 'Field1';
          Options := [ixPrimary];
        end;
        with AddIndexDef do
        begin
          Name := 'Fld2Indx';
          Fields := 'Field2';
          Options := [ixCaseInsensitive];
        end;
      end;
      { Call the CreateTable method to create the table }
      CreateTable;
      Table1.Active:= True;
      for i := 1 to 20 do
        Table1.AppendRecord([i*111, i*222]);
    end;
  end;
  DS2.DataSet:= Table1;
  DBGrid2.DataSource.DataSet:= Table1;
  Table1.Active:= True;
end;

Copy Code

{
This example uses the IndexName property to sort the records
in a client dataset on the Field2 field.
}
procedure TForm1.Button3Click(Sender: TObject);
var
  I : Integer;
begin
  // If Active is True, Update will remove Fields added in FormCreate
  // and add the DEFAULT_ORDER and CHANGEINDEX Fields
  CDS2.Active := False;
  { Get the current available indices }
  CDS2.IndexDefs.Update;
  { Find a field named 'Field2' }
  for I := 0 to CDS2.IndexDefs.Count - 1 do
    if CDS2.IndexDefs.Items[I].Fields = 'Field2' then
    begin
      { set that index as the current index for the dataset}
      CDS2.IndexName := CDS2.IndexDefs.Items[I].Name;
    end;
  CDS2.Active := True;
end;