mt5-manager/docs/publish/code/09_cpp.txt

ResetLastError();

if(!DatabaseTransactionBegin(g_db))
  {
   DatabaseFinalize(request);
   return false;
  }

DatabaseRead(request);
const int error = GetLastError();
DatabaseFinalize(request);

if(error != 0 && error != ERR_DATABASE_NO_MORE_DATA)
  {
   DatabaseTransactionRollback(g_db);
   return false;
  }

if(!DatabaseTransactionCommit(g_db))
   return false;