d-stream

select * from rooms where rooms.id_room_size not in (
select id_room_size from hotel.roomsize
)

using (SqlConnection conn = new SqlConnection(connectionString)) {
            using (SqlCommand cmd = new SqlCommand(commandText, conn)) {
               // There're three command types: StoredProcedure, Text, TableDirect. The TableDirect 
               // type is only for OLE DB.  
               cmd.CommandType = commandType;
               cmd.Parameters.AddRange(parameters);

               conn.Open();
               return cmd.ExecuteNonQuery();
            }
         }

public void ReadMyData(string myConnString)
{
  string mySelectQuery = "SELECT DeptNo, DName FROM Dept";
  SQLiteConnection sqConnection = new SQLiteConnection(myConnString);
  SQLiteCommand sqCommand = new SQLiteCommand(mySelectQuery,sqConnection); // команда конструируется с указанием соединения!!!
  sqConnection.Open();
  SQLiteDataReader sqReader = sqCommand.ExecuteReader();
  try
  {
    while (sqReader.Read())
    {
      Console.WriteLine(sqReader.GetInt32(0).ToString() + ", " + sqReader.GetString(1));
    }
  }
  finally
  {
  // always call Close when done reading.
  sqReader.Close();
  // always call Close when done reading.
  sqConnection.Close();
  }
}

select top 1 keys from (
SELECT RelPage_Y AS RP
FROM Keys
WHERE (((Keys.mp_group)=388))
UNION ALL SELECT RelPage_G AS RP
FROM Keys
WHERE (((Keys.mp_group)=388))
)
group by RP
order by count(RP) desc