增加2个#import，
#import "C:Program FilesCommon FilesSystemadomsado27.tlb" no_namespace rename("EOF","adoEOF")
#import "C:Program FilesCommon FilesSystemadomsjro.dll"
增加从QString到BSTR的转换函数
static inline BSTR QStringToBSTR(const QString &str)
{
return SysAllocStringLen((OLECHAR*)str.unicode(), str.length());
}
以下主要代码，注意在srcConnection和desConnection不能指向同一个数据源。
//compact the db
JRO::IJetEnginePtr jet(__uuidof(JRO::JetEngine));
QApplication::setOverrideCursor(QCursor(Qt::WaitCursor));
QString srcConnection=QString("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=%1;")
.arg(dbqPath);
QString desConnection=QString("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=%1;")
.arg(dbqPath+".tmp");
jet->CompactDatabase(QStringToBSTR(srcConnection), QStringToBSTR(desConnection));
bool renameError=false;
if ( !QFile::rename(dbqPath, dbqPath+"k")) renameError=true;
if (!QFile::rename(dbqPath+".tmp", dbqPath)) renameError=true;QApplication::restoreOverrideCursor();