DELPHI中操作ACCESS技巧集 - Delphi K.Top 討論區

發表時間：2004-02-08 13:19:36

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作者︰cwxiao888 來源︰不詳以下代碼在WIN2K,D6,MDAC2.6下測試通過, 編譯好的程式在WIN98第二版無ACCESS環境下執行成功. //在之前uses ComObj,ActiveX //聲明連接字串 Const SConnectionString = 'Provider=Microsoft.Jet.OLEDB.4.0;Data Source=%s;' 'Jet OLEDB:Database Password=%s;'; //============================================================================= // Procedure: GetTempPathFileName // Author : ysai // Date : 2003-01-27 // Arguments: (None) // Result : string //============================================================================= function GetTempPathFileName():string; //取得臨時檔案名 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; //壓縮與修複數據庫,覆寫來源檔案 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. 字分段名稱為關鍵字的字段用方括號[]括起來,數字作為字分段名稱也可行. 建立索引: 下面的語句在Tab1的Date列上建立可重複索引 Create Index iDate ON Tab1 ([Date]); 完成后ACCESS中字段Date索引屬性顯示為 - 有(有重複). 下面的語句在Tab1的Name列上建立不可重複索引 Create Unique Index iName ON Tab1 (Name); 完成后ACCESS中字段Name索引屬性顯示為 - 有(無重複). 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,所有引言的表都列在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; 存取多個不同的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語句查詢出目前數據庫中Tab1和db2.mdb(目前資料夾中)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中存取其它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可以在系統登錄中的 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支援子查詢 ACCESS支援外連接,但不內含完整外部聯接,如支援 LEFT JOIN 或 RIGHT JOIN 但不支援 FULL OUTER JOIN 或 FULL JOIN ACCESS中的日期查詢注意:ACCESS中的日期時間分隔字元是#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)])); ACCESS中的字串可以用雙引號分隔,但SQLSERVER不認,所以為了遷移方便和相容, 建議用單引號作為字串分隔字元.