//============================================================================= // Procedure: GetTempPathFileName // Author : ysai // Date : 2003-01-27 // Arguments: (None) // Result : string //============================================================================= function GetTempPathFileName():string; //取得臨時文件名 var SPath,SFile:array [0..254] of char; begin GetTempPath(254,SPath); GetTempFileName(SPath,'~SM',0,SFile); result:=SFile; DeleteFile(PChar(result)); end;
//============================================================================= // Procedure: CreateAccessFile // Author : ysai // Date : 2003-01-27 // Arguments: FileName:String;PassWord:string='' // Result : boolean //============================================================================= function CreateAccessFile(FileName:String;PassWord:string=''):boolean; //建立Access文件，如果文件存在則失敗 var STempFileName:string; vCatalog:OleVariant; begin STempFileName:=GetTempPathFileName; try vCatalog:=CreateOleObject('ADOX.Catalog'); vCatalog.Create(format(SConnectionString,[STempFileName,PassWord])); result:=CopyFile(PChar(STempFileName),PChar(FileName),True); DeleteFile(STempFileName); except result:=false; end; end;
//============================================================================= // Procedure: CompactDatabase // Author : ysai // Date : 2003-01-27 // Arguments: AFileName,APassWord:string // Result : boolean //============================================================================= function CompactDatabase(AFileName,APassWord:string):boolean; //壓縮與修復數據庫,覆蓋源文件 var STempFileName:string; vJE:OleVariant; begin STempFileName:=GetTempPathFileName; try vJE:=CreateOleObject('JRO.JetEngine'); vJE.CompactDatabase(format(SConnectionString,[AFileName,APassWord]), format(SConnectionString,[STempFileName,APassWord])); result:=CopyFile(PChar(STempFileName),PChar(AFileName),false); DeleteFile(STempFileName); except result:=false; end; end;
//============================================================================= // Procedure: ChangeDatabasePassword // Author : ysai // Date : 2003-01-27 // Arguments: AFileName,AOldPassWord,ANewPassWord:string // Result : boolean //============================================================================= function ChangeDatabasePassword(AFileName,AOldPassWord,ANewPassWord:string):boolean; //修改ACCESS數據庫密碼 var STempFileName:string; vJE:OleVariant; begin STempFileName:=GetTempPathFileName; try vJE:=CreateOleObject('JRO.JetEngine'); vJE.CompactDatabase(format(SConnectionString,[AFileName,AOldPassWord]), format(SConnectionString,[STempFileName,ANewPassWord])); result:=CopyFile(PChar(STempFileName),PChar(AFileName),false); DeleteFile(STempFileName); except result:=false; end; end;
2.ACCESS中使用SQL語句應注意的地方及幾點技巧 以下SQL語句在ACCESS XP的查詢中測試通過 建表: Create Table Tab1 ( ID Counter, Name string, Age integer, [Date] DateTime); 技巧: 自增字段用 Counter 聲明. 字段名為關鍵字的字段用方括號[]括起來,數字作為字段名也可行.
建立索引: 下面的語句在Tab1的Date列上建立可重復索引 Create Index iDate ON Tab1 ([Date]); 完成后ACCESS中字段Date索引屬性顯示為 - 有(有重復). 下面的語句在Tab1的Name列上建立不可重復索引 Create Unique Index iName ON Tab1 (Name); 完成后ACCESS中字段Name索引屬性顯示為 - 有(無重復). 下面的語句刪除剛才建立的兩個索引 Drop Index iDate ON Tab1; Drop Index iName ON Tab1;
ACCESS與SQLSERVER中的UPDATE語句對比: SQLSERVER中更新多表的UPDATE語句: UPDATE Tab1 SET a.Name = b.Name FROM Tab1 a,Tab2 b WHERE a.ID = b.ID; 同樣功能的SQL語句在ACCESS中應該是 UPDATE Tab1 a,Tab2 b SET a.Name = b.Name WHERE a.ID = b.ID; 即:ACCESS中的UPDATE語句沒有FROM子句,所有引用的表都列在UPDATE關鍵字后. 上例中如果Tab2可以不是一個表,而是一個查詢,例: UPDATE Tab1 a,(Select ID,Name From Tab2) b SET a.Name = b.Name WHERE a.ID = b.ID;
訪問多個不同的ACCESS數據庫-在SQL中使用In子句: Select a.*,b.* From Tab1 a,Tab2 b In 'db2.mdb' Where a.ID=b.ID; 上面的SQL語句查詢出當前數據庫中Tab1和db2.mdb(當前文件夾中)中Tab2以ID為關聯的所有記錄. 缺點-外部數據庫不能帶密碼. 補充:看到ugvanxk在一貼中的答復,可以用 Select * from [c:/aa/a.mdb;pwd=1111].table1; ACCESS XP測試通過
在ACCESS中訪問其它ODBC數據源 下例在ACCESS中查詢SQLSERVER中的數據 SELECT * FROM Tab1 IN [ODBC] [ODBC;Driver=SQL Server;UID=sa;PWD=;Server=127.0.0.1;DataBase=Demo;] 外部數據源連接屬性的完整參數是: [ODBC;DRIVER=driver;SERVER=server;DATABASE=database;UID=user;PWD=password;] 其中的DRIVER=driver可以在注冊表中的 HKEY_LOCAL_MACHINE/SOFTWARE/ODBC/ODBCINST.INI/ 中找到 異構數據庫之間導數據參見 碧血劍 的 http://www.delphibbs.com/delphibbs/dispq.asp?lid=1691966
ACCESS支持子查詢
ACCESS支持外連接,但不包括完整外部聯接,如支持 LEFT JOIN 或 RIGHT JOIN 但不支持 FULL OUTER JOIN 或 FULL JOIN
ACCESS中的日期查詢 注意:ACCESS中的日期時間分隔符是#而不是引號 Select * From Tab1 Where [Date]>#2002-1-1#; 在DELPHI中我這樣用 SQL.Add(Format( 'Select * From Tab1 Where [Date]>#%s#;', [DateToStr(Date)]));
