此程式是寫的一個Demo, 包含一個主窗體, 一個數據模組.

1. 主窗體設計如下:

提供一個初始化, 一個查詢, 一個釋放.

初始化用於資料模組例項化, 查詢就是執行SQL語句, 釋放就是釋放資料模組例項. 其它沒啥說的.

窗體上方是一個RadioGroup, 丟了四個按鈕, 也就是四個資料庫型別, 每個按鈕控制元件的TAG分別設定了0123, 用於資料庫連線切換方式的切換..

窗體左下方是四個SQL語句, 分別對應了四個資料庫.

2. 資料模組設計如下:

首先, 在程式根目錄下新建一個記事本, 重新命名為Driver.ini, 內容如下:

[MSSQL_Pool]
DriverID=MSSQL
Pooled=True
Server=192.168.2.188
Database=yqsh_SmartTable
User_Name=sa
Password=123
POOL_CleanupTimeout=0
POOL_ExpireTimeout=0
POOL_MaximumItems=50
CharacterSet=UTF8
 
[MySQL_Pool]
DriverID=MySQL
Pooled=True
Database=ungsm
User_Name=root
Password=1234
POOL_CleanupTimeout=0
POOL_ExpireTimeout=0
POOL_MaximumItems=50
Server=192.168.2.188
UseSSL=True
CharacterSet=utf8
 
[SQLite_Pool]
Pooled=True
Database=smarttable.db
POOL_MaximumItems=10
DriverID=SQLite
 

可以看出, 有三種連線方式, 分別是MSSQL_Pool, MySQL_Pool,SQLite_Pool, 分別對應三種資料庫連線, 這個名字是自定義的.

如果不知道這些引數怎麼來, 可以在資料模組丟一個TFDConnection控制元件(最後刪除掉), 雙擊控制元件, 如下圖所示:

然後配置引數, 然後再點選[Info], 如下入所示:

上圖選中部分其實就是Driver.ini中的配置引數, 拷貝出來, 自定義一個節點(比如: MSSQL_Pool)就好了.

然後再說下資料模組中的控制元件:

TFDManager 設定屬性ConnectionDefFileName, 這個設定Driver.ini的路徑就可以了, 因為Driver.ini就在根目錄下, 就直接寫Driver.ini就可以了, 設定FetchOptions.Mode為fmAll.

TFDConnection 設定FetchOptions.Mode為fmAll. ConnectionDefName動態指定.

TFDQuery 設定connection屬性, 下拉選擇TFDConnection即可.

TFDGUIxWaitCursor 丟一個

TFDPhysMSSQLDriverLink 丟一個 連線驅動

TFDPhysMySQLDriverLink 丟一個 連線驅動

TFDPhysSQLiteDriverLink 丟一個 連線驅動

TFDPhysOracleDriverLink 丟一個 連線驅動

3. 主窗程式碼如下:

unit uFrmMain;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ComCtrls, Vcl.ExtCtrls;
 
type
  TForm1 = class(TForm)
    mm1: TMemo;
    Button4: TButton;
    Button5: TButton;
    Button6: TButton;
    RadioGroup1: TRadioGroup;
    RadioButton1: TRadioButton;
    RadioButton2: TRadioButton;
    RadioButton3: TRadioButton;
    RadioButton4: TRadioButton;
    Label1: TLabel;
    Label2: TLabel;
    mm2: TMemo;
    Label3: TLabel;
    mm3: TMemo;
    Label4: TLabel;
    mm4: TMemo;
    procedure Button4Click(Sender: TObject);
    procedure Button6Click(Sender: TObject);
    procedure Button5Click(Sender: TObject);
    procedure RadioButtonClick(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
 
implementation
 
uses uDM_DAC;
 
{$R *.dfm}
 
procedure TForm1.Button4Click(Sender: TObject);
begin
  if not Assigned(dm) then
    dm:= TDM.Create(nil);
end;
 
procedure TForm1.Button5Click(Sender: TObject);
begin
  if not Assigned(dm) then
    Exit;
  if not dm.FDConnection.Connected then
    dm.FDConnection.Connected:= True;   //在連線池裡獲取一個連線
  with dm.FDQuery do
  begin
    Close;
    Case DM.FDBLX of
      0: SQL.Text:= mm1.Lines.Text;
      1: SQL.Text:= mm2.Lines.Text;
      2: SQL.Text:= mm3.Lines.Text;
      3: SQL.Text:= mm4.Lines.Text;
    End;
    Open;
  end;
  ShowMessage(IntToStr(dm.FDQuery.RecordCount));
  DM.FDConnection.Connected:= False;  //歸還連線 不是斷開
end;
 
procedure TForm1.Button6Click(Sender: TObject);
begin
  if Assigned(dm) then
    FreeAndNil(dm);
end;
 
procedure TForm1.RadioButtonClick(Sender: TObject);
begin
  if not Assigned(dm) then
  begin
    ShowMessage('資料模組未初始化!');
    Exit;
  end;
  if DM.DBChanged(TRadioButton(Sender).Tag) then
    ShowMessage('資料庫連線切換成功!')
  else
    ShowMessage('資料庫連線切換失敗!');
end;
 
end.
 

4. 資料模組程式碼如下:

unit uDM_DAC;
 
interface
 
uses
  SysUtils, Classes, FireDAC.Stan.Intf, FireDAC.Stan.Option, FireDAC.Stan.Error,
  FireDAC.UI.Intf, FireDAC.Phys.Intf, FireDAC.Stan.Def, FireDAC.Phys,
  FireDAC.Comp.Client, FireDAC.Phys.MSSQLDef, FireDAC.Phys.ODBCBase,
  FireDAC.Phys.MSSQL, FireDAC.VCLUI.Wait, FireDAC.Comp.UI, FireDAC.Stan.Pool,
  FireDAC.Stan.Async, Data.DB, FireDAC.Stan.Param, FireDAC.DatS,
  FireDAC.DApt.Intf, FireDAC.DApt, FireDAC.Comp.DataSet, FireDAC.Phys.MySQLDef,
  FireDAC.Phys.MySQL, FireDAC.Stan.ExprFuncs, FireDAC.Phys.SQLiteDef,
  FireDAC.Phys.SQLite, FireDAC.Phys.OracleDef, FireDAC.Phys.Oracle;
 
type
  TDM = class(TDataModule)
    FDManager: TFDManager;
    SQLLink: TFDPhysMSSQLDriverLink;
    WaitCursor: TFDGUIxWaitCursor;
    FDConnection: TFDConnection;
    FDQuery: TFDQuery;
    MYSQLLINK: TFDPhysMySQLDriverLink;
    SQLITELINK: TFDPhysSQLiteDriverLink;
    ORACLELINK: TFDPhysOracleDriverLink;
    procedure DataModuleCreate(Sender: TObject);
  private
    { Private declarations }
    function GetCode(iType: Integer; var sCode: string): Boolean;
  public
    { Public declarations }
    //0 Sqlserver 1 Mysql 2 Sqlite 3 Oracle 預設0
    FDBLX: Integer;
    function DBChanged(iType: integer): Boolean;
  end;
 
var
  DM: TDM;
 
implementation
 
{$R *.dfm}
 
procedure TDM.DataModuleCreate(Sender: TObject);
begin
  FDBLX:= 0;
  FDConnection.ConnectionDefName:= 'MSSQL_Pool';
end;
 
function TDM.DBChanged(iType: integer): Boolean;
var
  sCode: string;
begin
  Result:= False;
  if iType= FDBLX then
  begin
    Result:= True;
    Exit;
  end;
  try
    if GetCode(iType, sCode) then
    begin
      FDConnection.ConnectionDefName:= sCode;
      FDBLX:= iType;
      Result:= True;
    end;
  except
    on e: Exception do
      Exit;
  end;
end;
 
function TDM.GetCode(iType: Integer; var sCode: string): Boolean;
begin
  Result:= False;
  case iType of
    0: begin
      sCode:= 'MSSQL_Pool';
      Result:= True;
    end;
    1: begin
      sCode:= 'MySQL_Pool';
      Result:= True;
    end;
    2: begin
      sCode:= 'SQLite_Pool';
      Result:= True;
    end;
    3: begin
      sCode:= 'Oracle_Pool';
      Result:= True;
    end;
  else
    //
  end;
end;
 
end.

需要注意的是, 連線MySQL的時候, 還需要兩個dll驅動, 在原始碼連線裡有.

由於本機沒有安裝Oracle, 就沒有寫Oracle的連線了