FireDAC 下的 Sqlite [4] - 创建数据库

建立数据库的代码:

---

{建立内存数据库的一般代码:}
begin
  FDConnection1.DriverName := 'SQLite'; //同 FDConnection1.Params.Add('DriverID=SQLite');
//  FDConnection1.Params.Add('Database=:memory:'); //可省略这行, FireDAC 的源码显示, if Database = '' then Database := ':memory:';
//  FDConnection1.Params.Add('SQLiteAdvanced=page_size=4096'); //可指定内存页大小, 这是默认值
  FDConnection1.Connected := True;
end

{建立文件数据库的一般代码:}
begin
  FDConnection1.Params.Add('DriverID=SQLite');
  FDConnection1.Params.Add('Database=C:\Temp\New1.sdb'); //如果文件存在就打开, 不存在就建立
//  FDConnection1.Params.Add('SQLiteAdvanced=temp_store=Memory'); //可强制临时文件在内存以提高效率. 0:DEFAULT; 1:FILE; 2:MEMORY
//  FDConnection1.Params.Add('SQLiteAdvanced=temp_store_directory=C:\Temp'); //默认的临时文件路径应该是 C:\Documents and Settings\user-name\Local Settings\Temp\
//  FDConnection1.Params.Add('OpenMode=CreateUTF8'); //默认是 CreateUTF8, 也可选择 CreateUTF16
//  FDConnection1.Params.Add('LockingMode=Normal'); //默认是多用户模式, 如果使用独占模式 LockingMod=Exclusive 会更有效率
  FDConnection1.Connected := True;
end;

---

所有建立参数参见: http://www.sqlite.org/pragma.html

---

先在空白窗体上添加: TFDConnection、TFDPhysSQLiteDriverLink、TFDGUIxWaitCursor; 数据库的建立主要通过 TFDConnection 完成.

同时添加用于呈现数据的 TFDQuery、TDataSource、TDBGrid, 还要添加一个 TFDCommand 用于提交建表命令, 然后调整如下属性:

FDQuery1    . Connection = FDConnection1
DataSource1 . DataSet    = FDQuery1
DBGrid1     . DataSource = DataSource1
FDCommand1  . Connection = FDConnection1

你可以复制下面文本框中的内容, 然后直接往窗体上贴, 以快速完成以上的添加过程:

---

测试代码:

---

procedure TForm1.FormCreate(Sender: TObject);
const
  dbPath = 'C:\Temp\SQLiteTest.sdb';
begin
  if FileExists(dbPath) then DeleteFile(dbPath);

  with FDConnection1 do begin
    Params.Add('DriverID=SQLite');
    Params.Add('Database=' + dbPath);
    Connected := True;
  end;

  {创建一个名为 MyTable 的表, 字段包括: ID, Name, Age, Note, Picture}
  with FDCommand1.CommandText do begin
    Add('CREATE TABLE MyTable(');
    Add('ID integer PRIMARY KEY,'); //Integer 类型, 同时设为主键
    Add('Name string(10),');        //能容下 10 个字符的 String 类型
    Add('Age byte,');               //Byte 类型
    Add('Note text,');              //Memo 类型
    Add('Picture blob');            //Blob(二进制)类型
    Add(')');
  end;
  FDCommand1.Active := True;

  {查看表}
  FDQuery1.Open('SELECT * FROM MyTable');
end;

---

效果图:

---

直接使用 TFDConnection 提交 DDL 命令更简单:

---

procedure TForm1.FormCreate(Sender: TObject);
const
  dbPath = 'C:\Temp\SQLiteTest.sdb';
begin
  if FileExists(dbPath) then DeleteFile(dbPath);

  with FDConnection1 do begin
    Params.Add('DriverID=SQLite');
    Params.Add('Database=' + dbPath);
    Connected := True;
  end;

  {创建一个名为 MyTable 的表, 字段包括: ID, Name, Age, Note, Picture}
  FDConnection1.ExecSQL('CREATE TABLE MyTable(ID integer PRIMARY KEY, Name string(10), Age byte, Note text, Picture blob)');

  {查看表}
  FDQuery1.Open('SELECT * FROM MyTable');
end;

---

使用 SQLite 底层包装完成的建表提交(这样应该更有效率):

---

uses FireDAC.Phys.SQLiteWrapper; //为使用 TSQLiteStatement

{使用 TSQLiteStatement 完成的提交 SQL 命令的函数}
procedure MyExecSQL(ACon: TFDConnection; const ASQL: String);
begin
  with TSQLiteStatement.Create(ACon.CliObj) do
  try
    Prepare(ASQL);
    Execute;
    while PrepareNextCommand do Execute;
  finally
    Free;
  end;
end;

procedure TForm1.FormCreate(Sender: TObject);
const
  dbPath = 'C:\Temp\SQLiteTest.sdb';
begin
  if FileExists(dbPath) then DeleteFile(dbPath);

  with FDConnection1 do begin
    Params.Add('DriverID=SQLite');
    Params.Add('Database=' + dbPath);
    Connected := True;
  end;

  {创建一个名为 MyTable 的表, 字段包括: ID, Name, Age, Note, Picture}
  MyExecSQL(FDConnection1, 'CREATE TABLE MyTable(ID integer PRIMARY KEY, Name string(10), Age byte, Note text, Picture blob)');

  {查看表}
  FDQuery1.Open('SELECT * FROM MyTable');
end;

---

关于数据类型, SQLite 本身只支持(Null, Integer, Real, Text, Blob), 但我们可以放心使用 Delphi 的大多数类型(也包括 Delphi 没有的), 因为 FireDAC 幕后做了转换工作.

SQLite 到 FireDAC 数据类型映射表: (http://docwiki.embarcadero.com/RADStudio/XE6/en/Using_SQLite_with_FireDAC)

Type name	Description
rowid | _rowid_ | oid	dtInt64, Attrs = [caSearchable, caAllowNull, caROWID]
bit | bool | boolean | logical | yesno	dtBoolean
tinyint | shortint | int8 [unsigned]	dtSByte / dtByte
byte | uint8	dtByte
smallint | int16 [unsigned]	dtInt16 / dtUInt16
word | uint16 | year	dtUInt16
mediumint | integer | int | int32 [unsigned]	dtInt32 / dtUInt32
longword | uint32	dtUInt32
bigint | int64 | counter | autoincrement | identity [unsigned]	dtInt64 / dtUInt64
longlongword | uint64	dtUInt64
real | float | double	dtDouble
single [precision] [(p, s)]	dtSingle / dtBCD / dtFmtBCD
decimal | dec | numeric | number [unsigned] [(p, s)]	dtSByte / dtInt16 / dtInt32 / dtInt64  dtByte / dtUInt16 / dtUInt32 / dtUInt64  dtBCD / dtFmtBCD
money | smallmoney | currency | financial [(p, s)]	dtCurrency
date | smalldate	dtDate
datetime | smalldatetime	dtDateTime
timestamp	dtDateTimeStamp
time	dtTime
char | character [(l)]	dtAnsiString, Len = L, Attrs = [caFixedLen]
varchar | varchar2 | tynitext | character varying | char varying [(l)]	dtAnsiString, Len = L
nchar | national char | national character [(l)]	dtWideString, Len = L, Attrs = [caFixedLen]
nvarchar | nvarchar2 | national char varying | string [(l)]	dtWideString, Len = L
raw | tyniblob | varbinary | binary | binary varying [(l)]	dtByteString, Len = L
blob | mediumblob | image | longblob | long binary | long raw | longvarbinary | general | oleobject | tinyblob	dtBlob
mediumtext | longtext | clob | memo | note | long | long text | longchar | longvarchar | tinytext	dtMemo
text | ntext | wtext | nclob | nmemo | long ntext | long wtext | national text | longwchar | longwvarchar | html	dtWideMemo
xmldata | xmltype | xml	dtXML
guid | uniqueidentifier	dtGUID
other data types	dtWideString