1.DELPHI中操作ACCESS数据库(建立.mdb文件,压缩数据库) 以下代码在WIN2K,D6,MDAC2.6下测试通过, 编译好的程序在WIN98第二版无ACCESS环境下运行成功.
//============================================================================= // Procedure: GetTempPathFileName // Author : ysai // Date : 2003-01-27 // Arguments: (None) // Result : string //============================================================================= function GetTempPathFileName():string; //取得临时文件名 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，如果文件存在则失败 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; //压缩与修复数据库,覆盖源文件 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数据库密码 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语句应注意的地方及几点技巧 以下SQL语句在ACCESS XP的查询中测试通过 建表: Create Table Tab1 ( ID Counter, Name string, Age integer, [Date] DateTime); 技巧: 自增字段用 Counter 声明. 字段名为关键字的字段用方括号[]括起来,数字作为字段名也可行.
建立索引: 下面的语句在Tab1的Date列上建立可重复索引 Create Index iDate ON Tab1 ([Date]); 完成后ACCESS中字段Date索引属性显示为 - 有(有重复). 下面的语句在Tab1的Name列上建立不可重复索引 Create Unique Index iName ON Tab1 (Name); 完成后ACCESS中字段Name索引属性显示为 - 有(无重复). 下面的语句删除刚才建立的两个索引 Drop Index iDate ON Tab1; Drop Index iName ON Tab1;
ACCESS与SQLSERVER中的UPDATE语句对比: SQLSERVER中更新多表的UPDATE语句:
访问多个不同的ACCESS数据库-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语句查询出当前数据库中Tab1和db2.mdb(当前文件夹中)中Tab2以ID为关联的所有记录. 缺点-外部数据库不能带密码. 补充:看到ugvanxk在一贴中的答复,可以用 Select * from [c:\aa\a.mdb;pwd=1111].table1; ACCESS XP测试通过
在ACCESS中访问其它ODBC数据源 下例在ACCESS中查询SQLSERVER中的数据
ACCESS支持子查询
ACCESS支持外连接,但不包括完整外部联接,如支持 LEFT JOIN 或 RIGHT JOIN 但不支持 FULL OUTER JOIN 或 FULL JOIN
ACCESS中的日期查询 注意:ACCESS中的日期时间分隔符是#而不是引号 Select * From Tab1 Where [Date]>#2002-1-1#; 在DELPHI中我这样用 SQL.Add(Format( 'Select * From Tab1 Where [Date]>#%s#;', [DateToStr(Date)]));
ACCESS中的字符串可以用双引号分隔,但SQLSERVER不认,所以为了迁移方便和兼容, 建议用单引号作为字符串分隔符.
