As I did not get any answer, I decided to split the two question so that they appear less daunting. The initial question I am referring to is this one
Here is a table with regular alignment mixed with dec sep align:
\documentclass{article}
\usepackage{pgfplotstable}
\usepackage{booktabs}
\begin{document}
\pgfplotstabletypeset[%
col sep=&, header=false,
every head row/.style={before row={\toprule%
\multicolumn{1}{l}{a} & \multicolumn{1}{l}{b} & \multicolumn{1}{l}{c} & \multicolumn{2}{l}{ddd ddd ddd}\\
% \multicolumn{2}{l}{Glonk}\\
}, after row={\midrule}
},
every last row/.style={after row=\bottomrule},
display columns/0/.style={column name={Grandeur}, string type, column type={l}},
display columns/1/.style={column name={Unite}, string type, column type={l}},
display columns/2/.style={column name={Reference}, dec sep align={l}},
display columns/3/.style={column name={Reference}, dec sep align={l}},
display columns/4/.style={column name={Reference}, dec sep align={l}},
]
{%
glonk & z & 323.1 & 323.1 & 323.1
plokt & y & 33.12 & 33.12 & 33.12
jlorp & x & 3.123 & 3.123 & 3.123
}
\end{document}
And here is what it produces:

Somehow the width of the columns are incorrectly accounted for when
using dec sep align.
How could I correct this strange behaviour.
\multicolumn{1}{l}{a} & \multicolumn{1}{l}{b} & \multicolumn{2}{l}{c} & \multicolumn{4}{l}{ddd ddd ddd}\\solved the problem.
Maybe you can put this into an answer that I will be glad to accept?
– M. Toya Sep 27 '12 at 08:50