%%
%% The LaTeX Companion, 3ed
%%
%% Example 6-9-7 on page I-503 in "Spanning cells".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3exa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{135.0pt}

  \setlength\tabcolsep{6pt}

  \usepackage{keyvaltable}
  \kvtSet{ColGroup/format=\itshape,ColGroup/align=r}
  \NewKeyValTable{spantest}{ colA: align=l|; colB: align=l||;
                             colC: align=l|; colD:}
        [ colgroups={ all: span=colA+colB+colC+colD, format=\textbf;
                    AuBuC: span=colA+colB+colC, align=c|;
                      AuB: span=colA+colB, align=l||;  CuD: span=colC+colD } ]

%StartShownPreambleCommands

%StopShownPreambleCommands

\begin{document}
\begin{KeyValTable}{spantest}
 \Row{all=The Start}  \Row{colA=1, colB=2, colC=3, colD=4}
 \Row{all=--- right aligned text ---}
 \Row{AuB=1 \& 2,       colC=3,  colD=4}
 \Row{colA=1, colB=2,   colC=3,  colD=4}
 \Row{colA=1, colB=2,    CuD=3 \& 4}
 \Row{AuBuC=--- 3 out of 4 ---,    colD=4}
 \Row{AuB=1 \& 2, CuD=3 \& 4} \Row{all=The End}
\end{KeyValTable}
\end{document}