As percusse said in his comment, the most convenient way to go is to exploit the tikzmark macro (just one reference: Adding a large brace next to a body of text).
This solution allows to draw both braces and arrows through:
\drawbrace command;
\drawcurvedarrow command,
as well as to put some annotations via \annote and it exploits a variant of tikzmark macro in which it is possible to customize a bit the position of the marker via shifts.
The code:
\documentclass[border=20pt,png]{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.pathreplacing,calc}
\newcommand{\tikzmark}[2][-3pt]{\tikz[remember picture, overlay, baseline=-0.5ex]\node[#1](#2){};}
\tikzset{brace/.style={decorate, decoration={brace}},
brace mirrored/.style={decorate, decoration={brace,mirror}},
}
\newcounter{brace}
\setcounter{brace}{0}
\newcommand{\drawbrace}[3][brace]{%
\refstepcounter{brace}
\tikz[remember picture, overlay]\draw[#1] (#2.center)--(#3.center)node[pos=0.5, name=brace-\thebrace]{};
}
\newcounter{arrow}
\setcounter{arrow}{0}
\newcommand{\drawcurvedarrow}[3][]{%
\refstepcounter{arrow}
\tikz[remember picture, overlay]\draw (#2.center)edge[#1]node[coordinate,pos=0.5, name=arrow-\thearrow]{}(#3.center);
}
% #1 options, #2 position, #3 text
\newcommand{\annote}[3][]{%
\tikz[remember picture, overlay]\node[#1] at (#2) {#3};
}
\begin{document}
\begin{tabular}{ | l | l |}
\hline
letter & number \\ \hline
\tikzmark[xshift=-8pt,yshift=1ex]{x}A & 1\tikzmark[xshift=3.5em]{a} \\ \hline
A & 2 \\ \hline
\tikzmark[xshift=-8pt,yshift=-1ex]{y}A & 1\tikzmark[xshift=3.5em]{b} \\ \hline
\tikzmark[xshift=-8pt,yshift=1ex]{w}B & 1 \\ \hline
\tikzmark[xshift=-8pt,yshift=-1ex]{z}B & 2 \\ \hline
\end{tabular}
\drawcurvedarrow[bend left=60,-stealth]{a}{b}
\drawbrace[brace mirrored, thick]{x}{y}
\drawbrace[brace mirrored, thick]{w}{z}
\annote[right]{arrow-1}{Duplicate}
\annote[left]{brace-1}{A}
\annote[left]{brace-2}{B}
\end{document}
The result:

Remember to compile at least twice to get the result and to put annotations refer to the order in which braces or arrows have been deployed to identify their position (i.e. second brace: brace-2, fourth arrow: arrow-4).
math tikzmark [tikz-pgf]on the top right corner. An example http://tex.stackexchange.com/questions/47610/how-to-draw-arrows-from-cell-to-cell-at-the-borders-of-a-table – percusse Jun 06 '13 at 08:52