%% 
%%  A DANTE-Edition example
%% 
%%  Example 02-26-4 on page 105.
%% 
%%  Copyright (C) 2010 Herbert Voss
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 
%% 
%% ==== 
% Show page(s) 1
%% 
\documentclass[]{article}
\pagestyle{empty}
\setlength\textwidth{177.70511pt}
\usepackage[utf8]{inputenc}

\usepackage[exponent-product=\cdot]{siunitx}
\sisetup{table-parse-only}
\usepackage{booktabs}

\begin{document}
\begin{tabular}{ S S[table-number-alignment=left]
  S[table-number-alignment=right]}\toprule
\emph{centred} & \emph{left-aligned}
  & \emph{right-aligned} \\\midrule
14.2    & 14.2    & 14.2 \\
1.23456 & 1.23456 & 1.23456\\
1.2e3   & 1.2e3   & 1.2e3\\\bottomrule
\end{tabular}
\end{document}

.
