FireDAC.AutoincFields Sample

This sample demonstrates how to implement auto-incremental fields using FireDAC.

Location

You can find the AutoincFields sample project at:

• Start | Programs | Embarcadero RAD Studio Rio | Samples and then navigate to:
  • Object Pascal\Database\FireDAC\Samples\DApt Layer\Autoinc fields
• Subversion Repository:
  • You can find Delphi code samples in GitHub Repositories. Search by name into the samples repositories according to your RAD Studio version.

Description

The AutoincFields sample shows you how to work with auto-incremental fields using FireDAC. To this end, the sample uses the TFDDatSColumn class to control the client-side and the server-side auto-incrementing fields. Concretely, the sample uses the TFDDatSColumn.ServerAutoIncrement property of TFDDatSColumn to specify when the DBMS generates an auto-incrementing value for the new record column.

How to Use the Sample

1. Navigate to the location given above and open AutoInc.dproj.
2. Press F9 or choose Run > Run.
3. Click on the Use Connection Definition combo box and select an option.

Files

File in Delphi	Contains
AutoInc.dproj AutoInc.dpr	The project itself.
fAutoInc.pas fAutoInc.fmx	The main form.

Implementation

The sample implements the following features.

Create schema adapter

To this end, the sample uses FDCreateInterface. See the following code:

  var
    oSchAdapt:  IFDDAptSchemaAdapter;
    // ...
  begin
    // create schema adapter
    FDCreateInterface(IFDDAptSchemaAdapter, oSchAdapt);

Add master table adapter

The sample adds the master table adapter and sets some configuration properties, such as the ServerAutoIncrement property. See the following code:

  var
    oMastAdapt:  IFDDAptTableAdapter;
    // ...
  begin  
    oMastAdapt := oSchAdapt.TableAdapters.Add(EncodeName('FDQA_master_autoinc'), 'master');
    with oMastAdapt do begin
      // ...
      with DatSTable.Columns[0] do
        ServerAutoIncrement := True;
      // ...
    end
    // ...

Note: setting the ServerAutoIncrement property to True automatically assigns the AutoIncrementSeed and AutoIncrementStep properties to -1.

Add detail table adapter

The sample adds a detail table adapter and sets up some features. To this end, the sample adds the following code:

  var
    oDetAdapt:  IFDDAptTableAdapter;
    // ...
  begin
    // ...
    oDetAdapt := oSchAdapt.TableAdapters.Add(EncodeName('FDQA_details_autoinc'), 'details');
    with oDetAdapt do begin
      // ...
      with DatSTable.Columns[0] do
        ServerAutoIncrement := True;
      // ...
    end
    //  ...

Add constraints to the DatSManager

To this end, the sample uses the Constraints property of TFDDatSTable. See the following code:

  with oSchAdapt.DatSManager.Tables.ItemsS['master'] do
    Constraints.AddUK('master_pk',  'parent_id', True);
  with oSchAdapt.DatSManager.Tables.ItemsS['details'] do begin
    Constraints.AddUK('details_pk', 'child_id',  True);
    with Constraints.AddFK('details_fk_master', 'master', 'parent_id', 'fk_parent_id') do begin
      UpdateRule := crCascade;
      DeleteRule := crCascade;
      AcceptRejectRule := arCascade;
    end;
  end;

Add new row to the master table

  oMastRow := oMastAdapt.DatSTable.Rows.Add([Unassigned, 'Master ' + IntToStr(Random(1000000000))]); // Set Unassigned for identity fields

Post changes to RDBMS

Finally, the sample updates the changes with the Update method. Then, the sample uses the Reconcile method to obtain the error information for each record that could not be applied.

  oSchAdapt.Update;
  oSchAdapt.Reconcile;

Uses

• FDCreateInterface
• TFDAutoIncField
  • ServerAutoIncrement
  • AutoIncrementSeed
  • AutoIncrementStep
• IFDPhysCommand
  • SelectCommand
• The sample also uses some properties such as Constraints of the following unit:
  • FireDAC.DatS
• The sample also uses some methods such as Update or Reconcile and some properties such as ColumnMapping of the following units:
  • FireDAC.DApt
  • FireDAC.DApt.Intf

See Also

• FireDAC
• FireDAC Data Adapter [DApt]
• Auto-Incremental Fields (FireDAC)

Samples

• FireDAC DAptLayer GettingStarted sample
• FireDAC DApt Layer Commands sample
• FireDAC Mapping Columns sample