constadOpenDynamic = $00000002;adOpenStatic = $00000003;adLockOptimistic = $00000003;adLockBatchOptimistic = $00000004;adStateClosed = $00000000;adStateOpen = $00000001;adStateConnecting = $00000002;adStateExecuting = $00000004;adStateFetching = $00000008;adUseServer = $00000002;adUseClient = $00000003;adModeReadWrite = $00000003;adXactCursorStability = $00001000;adCmdText = $00000001;adCmdTable = $00000002;adCmdStoredProc = $00000004;adCmdFile = $00000100;adAffectCurrent = $00000001;adAffectGroup = $00000002;adAffectAll = $00000003;adAffectAllChapters = $00000004;3、一些基本函数和过程
//创建 Connection 对象
function CreateConnection: OleVariant;
//释放 Connection 对象；cnn 为 Connection 对象
procedure FreeConnection(var cnn: OleVariant);
//创建 Recordset 对象
function CreateRecordset: OleVariant;
//释放 Recordset 对象；rst 为 Recordset 对象
procedure FreeRecordset(var rst: OleVariant);
//创建 Command 对象
function CreateCommand: OleVariant;
//释放 Command 对象；cmd 为 Command 对象
procedure FreeCommand(var cmd: OleVariant);
//用 Connection 连接到 SQLServer 数据库；cnn 为 Connection 对象，db 数据库名，host 主机名，usr 用户名，pwd 密码
function ConnectToDB(cnn: OleVariant; const db, host, usr, pwd: string): Boolean;
//执行 SQL 语句，有返回行，无事务处理；cnn 为 Connection 对象，rst 为 Recordset 对象，sql 为 SQL 语句（可以是存储过程）
function ExecSQL(cnn, rst: OleVariant; const sql: string): Boolean;
//执行 SQL 语句，无返回行，有事务处理；cnn 为 Connection 对象，cmd 为 Command 对象，sql 为 SQL 语句（可以是存储过程）
function ExecSQLA(cnn, cmd: OleVariant; const sql: string): Boolean;function CreateConnection: OleVariant;
begintryResult := CreateOleObject('ADODB.Connection');Result.CursorLocation := adUseServer;Result.IsolationLevel := adXactCursorStability;Result.Mode := adModeReadWrite;Result.Provider := 'SQLOLEDB.1';exceptif not VarIsEmpty(Result) then Result := Unassigned;end;
end;procedure FreeConnection(var cnn: OleVariant);
beginif not VarIsEmpty(cnn) thenbeginif cnn.State <> adStateClosed then cnn.Close;cnn := Unassigned;end;
end;function CreateRecordset: OleVariant;
begintryResult := CreateOleObject('ADODB.Recordset');Result.CacheSize := 1000;Result.CursorType := adOpenStatic;Result.CursorLocation := adUseServer;Result.LockType := adLockOptimistic;exceptif not VarIsEmpty(Result) then Result := Unassigned;end;
end;procedure FreeRecordset(var rst: OleVariant);
beginFreeConnection(rst);
end;function CreateCommand: OleVariant;
begintryResult := CreateOleObject('ADODB.Command');Result.CommandType := adCmdText;Result.CommandTimeout := 5;exceptif not VarIsEmpty(Result) then Result := Unassigned;end;
end;procedure FreeCommand(var cmd: OleVariant);
beginif not VarIsEmpty(cmd) then cmd := Unassigned;
end;function ConnectToDB(cnn: OleVariant; const db, host, usr, pwd: string): Boolean;
beginResult := not VarIsEmpty(cnn);if Result thenbeginif cnn.State <> adStateClosed then cnn.Close;cnn.ConnectionString :='Provider=SQLOLEDB.1;Persist Security Info=True;Initial Catalog=' +db + ';Data Source=' + host + ';Connect Timeout=5;' +'Use Procedure for Prepare=1';trycnn.Open(cnn.ConnectionString, usr, pwd, -1);exceptResult := False;end;end;
end;function ExecSQL(cnn, rst: OleVariant; const sql: string): Boolean;
beginResult := not (VarIsEmpty(cnn) or VarIsEmpty(rst)) and (cnn.State = adStateOpen);if Result thenbeginif rst.State <> adStateClosed then rst.Close;tryrst.Open(sql, cnn, adOpenStatic, adLockOptimistic, adCmdText);exceptResult := False;end;end;
end;function ExecSQLA(cnn, cmd: OleVariant; const sql: string): Boolean;
beginResult := not (VarIsEmpty(cnn) or VarIsEmpty(cmd)) and (cnn.State = adStateOpen);if Result thenbegincnn.BeginTrans;trycmd.ActiveConnection := cnn;cmd.CommandText := sql;cmd.Prepared := True;cmd.Execute;cnn.CommitTrans;exceptcnn.RollbackTrans;Result := False;end;end;
end;

//变量声明
varcnn, rst, cmd: OleVariant;//创建对象
procedure TForm1.FormCreate(Sender: TObject);
begincnn := CreateConnection;rst := CreateRecordset;cmd := CreateCommand;
end;//释放对象
procedure TForm1.FormDestroy(Sender: TObject);
beginFreeCommand(cmd);FreeRecordset(rst);FreeConnection(cnn);
end;//连接数据库
procedure TForm1.Button1Click(Sender: TObject);
beginif ConnectToDB(cnn, 'mydb', '127.0.0.1', 'sa', 'ok') thenCaption := '连接成功'else Caption := '连接失败';
end;//取记录
procedure TForm1.Button2Click(Sender: TObject);
beginExecSQL(cnn, rst, 'select * from 表a');Caption := VarToStr(rst.Fields['字段a'].Value);
end;

uses ComObj;
//Access
//TableName: 表名; OldColName: 原字段名; NewColName: 新字段名;
procedure RenameField(const TableName, OldColName, NewColName: string);
varDB, Col: OleVariant;
beginDB := CreateOleObject('ADOX.Catalog');DB.ActiveConnection := ADOConnection1.ConnectionObject;Col := CreateOleObject('ADOX.Column');Col := DB.Tables[TableName].Columns[OldColName];Col.Name := NewColName;
end;//SQLServer
procedure RenameField(const TableName, OldColName, NewColName: string);
beginwith ADOCommand1 dobeginCommandText := 'EXEC sp_rename ''' + TableName + '.' + OldColName + ''',''' + NewColName + ''',''COLUMN'';';Excute;end;
end;2、取得 Access 库中的表结构
typeTTableDef = recordName,DateCreated,LastUpdated,Description: string;end;TTableDefs = array of TTableDef;procedure GetTableDefs(const DBName: string; out TableDefs: TTableDefs);
varDBEngine, DB: OleVariant;I: Longint;
begintryDBEngine := CreateOleObject('DAO.DBEngine.36');DB := DBEngine.OpenDatabase(DBName);SetLength(TableDefs, Longint(DB.TableDefs.Count));for I := Low(TableDefs) to High(TableDefs) dobeginTableDefs[I].Name := DB.TableDefs[I].Name;TableDefs[I].DateCreated := DB.TableDefs[I].DateCreated;TableDefs[I].LastUpdated := DB.TableDefs[I].LastUpdated;tryTableDefs[I].Description := DB.TableDefs[I].Properties['Description'].Value;exceptTableDefs[I].Description := '';end;end;finallyDB := Unassigned;DBEngine := Unassigned;end;
end;3、取得 Access 表中的字段结构
typeTFieldDef = recordName: string;Types,Size: Longint;Description: string;end;TFieldDefs = array of TFieldDef;procedure GetFieldDefs(const DBName, TableName: string; out FieldDefs: TFieldDefs);
varDBEngine, DB: OleVariant;I: Longint;
begintryDBEngine := CreateOleObject('DAO.DBEngine.36');DB := DBEngine.OpenDatabase(DBName);SetLength(FieldDefs, Longint(DB.TableDefs[TableName].Fields.Count));for I := Low(FieldDefs) to High(FieldDefs) dobeginFieldDefs[I].Name := DB.TableDefs[TableName].Fields[I].Name;FieldDefs[I].Types := DB.TableDefs[TableName].Fields[I].Type;FieldDefs[I].Size := DB.TableDefs[TableName].Fields[I].Size;tryFieldDefs[I].Description := DB.TableDefs[TableName].Fields[I].Properties['Description'].Value;exceptFieldDefs[I].Description := '';end;end;finallyDB := Unassigned;DBEngine := Unassigned;end;
end;