Control order of columns in table

Using @MartinScharrer's rather new collcell package, we can collect the body of each cell and save it with a given label, then typeset the cells in a different order, calling each label. Namely, the code below defines two column types: s{<label>} (for save) and o{<label>} (for output).

One drawback is that you need to put a whole bunch of & at the end of each line to allow typesetting to occur (as many & as you have columns). This can also be used to e.g. double one column, or remove one column.

\documentclass{article}
\usepackage{collcell}
\usepackage{array}

\newcommand{\newcelltoksifnew}[1]{%
  \expandafter\ifx\csname cell@toks@#1\endcsname\relax
  \expandafter\newtoks\csname cell@toks@#1\endcsname
  \fi}
\newcolumntype{s}[1]{%
  >{\unskip\newcelltoksifnew{#1}%
    \collectcell{\global\csname cell@toks@#1\endcsname}}%
  c%
  <{\endcollectcell}%
  @{}%
}
\newcolumntype{o}[1]{%
  >{\the\csname cell@toks@#1\endcsname}%
  c%
}

\begin{document}
\begin{table}\centering
\begin{tabular}{|c|c|c|}
  a  &  c  &  b  \\
AAAAA&CCCCC&BBBBB
\end{tabular}

\begin{tabular}{s{A}s{B}s{C}|o{A}|o{C}|o{B}|}
  a  &  b  &  c  &&&\\
AAAAA&BBBBB&CCCCC&&&
\end{tabular}
\caption{Comparing two tables to see that the spacing is not affected.}
\end{table}

\end{document}

Another method would be to swap to column using a string manipulation package, let's say xstring ;). Of course, swapping 2 columns is not reorder all of them!

The \swapcol command must be written at the begining of every row in which you want to swap the content of 2 cells. The last row must be ended with a \\.

Here is the tricky code:

\documentclass[a4paper]{article}
\usepackage{xstring}
\usepackage{array}
\def\expaddtocs#1#2{%
    \expandafter\expandafter\expandafter\def\expandafter\expandafter\expandafter
    #1\expandafter\expandafter\expandafter{\expandafter#1#2}}
\def\swapcol#1#2#3\\{%
    \ifnum#1>#2 \def\colinf{#2}\def\colsup{#1}%
    \else \def\colinf{#1}\def\colsup{#2}\fi
    \noexpandarg \let\swaprow\empty \iffalse{\fi\ifnum0=`}\fi
    \expandafter\StrBefore\expandafter[\number\numexpr\colinf-1]{#3&}&[\beforecol]%
    \ifx\beforecol\empty\else\expaddtocs\swaprow{\beforecol&}\fi
    \StrBehind[\colinf]{&#3&}&[\aftercol]%
    \expandafter\StrBefore\expandafter{\aftercol}&[\colA]%
    \expandafter\StrBehind\expandafter{\aftercol}&[\aftercol]%
    \expandafter\StrBefore\expandafter[\number\numexpr\colsup-\colinf-1\expandafter]\expandafter{\aftercol}&[\intercol]%
    \StrBehind[\colsup]{&#3}&[\aftercol]%
    \expandafter\StrBefore\expandafter{\aftercol&}&[\colB]%
    \expandafter\StrBehind\expandafter{\aftercol}&[\aftercol]%
    \expaddtocs\swaprow{\colB&}%
    \ifx\intercol\empty\else\expaddtocs\swaprow{\intercol&}\fi
    \expaddtocs\swaprow{\colA}%
    \ifx\aftercol\empty\else\expaddtocs\swaprow{\noexpand&}\fi
    \expaddtocs\swaprow{\aftercol\\}%
    \ifnum0=`{\fi\iffalse}\fi \swaprow}

\begin{document}
\begin{tabular}{ccccc}
1 & 2 & 3 & 4 & 5 \\
1 & 2 & 3 & 4 & 5 \\
1 & 2 & 3 & 4 & 5 \\
\end{tabular}
\qquad
\begin{tabular}{ccccc}
\swapcol{2}{5}1 & 2 & 3 & 4 & 5 \\
\swapcol{2}{5}1 & 2 & 3 & 4 & 5 \\
\swapcol{2}{5}1 & 2 & 3 & 4 & 5 \\
\end{tabular}

\begin{tabular}{|c|c|c|}
  a  &  c  &  b  \\
AAAAA&CCCCC&BBBBB
\end{tabular}
\qquad
\begin{tabular}{|c|c|c|}
\swapcol{1}{2}  a  &  c  &  b  \\
\swapcol{1}{2}AAAAA&CCCCC&BBBBB\\
\end{tabular}
\end{document}