\t注释标记超出表格边框

Question

在使用时上threeparttable标\tnote超出表格边框：@{}

\documentclass{book}
\usepackage{booktabs}
\usepackage[flushleft]{threeparttable}
\begin{document}
\begin{threeparttable}
  \begin{tabular}{@{}ll@{}}
    \toprule
    First column header & Second column header\tnote{a}\\
    \midrule
    a & b \\
    c & d \\
    \bottomrule
    \end{tabular}
    \begin{tablenotes}
        \item[a] A note.
    \end{tablenotes}
\end{threeparttable}
\end{document}

如何避免？

Answer 1

由于 Ulrike 的解决方案仅增加了表格中一列的宽度，事后看来似乎不成比例，因此我尝试了另一种解决方案\phantom：

\documentclass{book}
\usepackage{booktabs}
\usepackage[flushleft]{threeparttable}
\usepackage{float}
\usepackage{caption}
\usepackage[margin=10pt,labelfont=bf,labelsep=period,format=hang,
indention=0cm]{caption}
\captionsetup[table]{position=above, aboveskip=2pt}

\begin{document}
\begin{table} 
    \centering
    \caption{Original table}
    \begin{threeparttable}
        \begin{tabular}{@{}ll@{}}
            \toprule
            First column header & Second column header\tnote{a}\\
            \midrule
            a & b \\
            c & d \\
            \bottomrule
        \end{tabular}
        \begin{tablenotes}
            \item[a] A note.
        \end{tablenotes}
    \end{threeparttable}
\end{table}
\begin{table}
    \centering
    \caption{Table with Ulrike's command}
    \begin{threeparttable}
        \let\TPTrlap\relax
        \begin{tabular}{@{}ll@{}}
            \toprule
            First column header & Second column header\tnote{a}\\
            \midrule
            a & b \\
            c & d \\
            \bottomrule
        \end{tabular}
        \begin{tablenotes}
            \item[a] A note.
        \end{tablenotes}
    \end{threeparttable}
\end{table}
\begin{table}
    \centering
    \caption{Table with one \textbackslash\texttt{panthom}}
    \begin{threeparttable}
        \begin{tabular}{@{}ll@{}}
            \toprule
            First column header & Second column header\tnote{a}\phantom{\textsuperscript{a}}\\
            \midrule
            a & b \\
            c & d \\
            \bottomrule
        \end{tabular}
        \begin{tablenotes}
            \item[a] This looks the same as Ulrike's table.
        \end{tablenotes}
    \end{threeparttable}
\end{table}
\begin{table}
    \centering
    \caption{Table with two \textbackslash\texttt{panthom}s}
    \begin{threeparttable}
        \begin{tabular}{@{}ll@{}}
            \toprule
            First column header\phantom{\textsuperscript{a}} & Second column header\tnote{a}\phantom{\textsuperscript{a}}\\
            \midrule
            a & b \\
            c & d \\
            \bottomrule
        \end{tabular}
        \begin{tablenotes}
            \item[a] This is the solution I prefer.
        \end{tablenotes}
    \end{threeparttable}
\end{table}
\begin{table}
    \centering
    \caption{Table without @\{\}}
    \begin{threeparttable}
        \begin{tabular}{ll}
            \toprule
            First column header & Second column header\tnote{a}\\
            \midrule
            a & b \\
            c & d \\
            \bottomrule
        \end{tabular}
        \begin{tablenotes}
            \item[a] This is the solution egreg and cfr prefer.
        \end{tablenotes}
    \end{threeparttable}
\end{table}
\end{document}