Difficulty in using multicolumn or multirow in tabularx

Question

I just started learning latex and needed a kind of table like what the uploaded picture shows. The code was generated by Excel2LaTex. I have tried some ways but cannot make it.

Several cells in the lower left corner of the table are merged. The command \tabular cannot make the table adaptively adjust the width to the whole row. If I use \resizebox, the height of the table will increase together, which will be very unsightly. So I used \tabularx but it always went wrong...Although I knew that \tabular cannot be simply replaced by \tabularx, I had no idea dealing with it...

So I come here for help. By the way, if it is really difficult, the big fork in the big cell can not be used. After all, this is drawn by Excel and it is very simple there.

\begin{table}[htbp]
  \centering
  \caption{Add caption}
    \begin{tabular}{|c|c|c|c|c|c|}
    \hline
    order & number & weight & order & number & weight \\
    \hline
    1     & 1     & 1     & 1     & 1     & 1 \\
    \hline
    2     & 2     & 2     & 2     & 2     & 2 \\
    \hline
    3     & 3     & 3     & 3     & 3     & 3 \\
    \hline
    ...   & ...   & ...   & ...   & ...   & ... \\
    \hline
    118   & 118   & 118   & 118   & 118   & 118 \\
    \hline
    119   & 119   & 119   & 119   & 119   & 119 \\
    \hline
    120   & 120   & 120   & 120   & 120   & 120 \\
    \hline
    \multicolumn{3}{|c|}{\multirow{4}[8]{*}{}} & ...   & ...   & ... \\
    \cline{4-6}    \multicolumn{3}{|c|}{}      & 138   & 138   & 138 \\
    \cline{4-6}    \multicolumn{3}{|c|}{}      & 139   & 139   & 139 \\
    \cline{4-6}    \multicolumn{3}{|c|}{}      & 140   & 140   & 140 \\
    \hline
    \end{tabular}%
  \label{tab:addlabel}%
\end{table}%

I also tried tablesgenerator website. It gave me the following code:

% Please add the following required packages to your document preamble:
% \usepackage{multirow}
\begin{table}[]
\caption{}
\label{tab:my-table}
\begin{tabular}{|ccc|c|c|c|}
\hline
\multicolumn{1}{|c|}{order} & \multicolumn{1}{c|}{number} & weight & order & number & weight \\ \hline
\multicolumn{1}{|c|}{1}     & \multicolumn{1}{c|}{1}      & 1      & 1     & 1      & 1      \\ \hline
\multicolumn{1}{|c|}{2}     & \multicolumn{1}{c|}{2}      & 2      & 2     & 2      & 2      \\ \hline
\multicolumn{1}{|c|}{3}     & \multicolumn{1}{c|}{3}      & 3      & 3     & 3      & 3      \\ \hline
\multicolumn{1}{|c|}{...}   & \multicolumn{1}{c|}{...}    & ...    & ...   & ...    & ...    \\ \hline
\multicolumn{1}{|c|}{118}   & \multicolumn{1}{c|}{118}    & 118    & 118   & 118    & 118    \\ \hline
\multicolumn{1}{|c|}{119}   & \multicolumn{1}{c|}{119}    & 119    & 119   & 119    & 119    \\ \hline
\multicolumn{1}{|c|}{120}   & \multicolumn{1}{c|}{120}    & 120    & 120   & 120    & 120    \\ \hline
\multicolumn{3}{|c|}{\multirow{4}{*}{}}                            & ...   & ...    & ...    \\ \cline{4-6} 
\multicolumn{3}{|c|}{}                                             & 138   & 138    & 138    \\ \cline{4-6} 
\multicolumn{3}{|c|}{}                                             & 139   & 139    & 139    \\ \cline{4-6} 
\multicolumn{3}{|c|}{}                                             & 140   & 140    & 140    \\ \hline
\end{tabular}
\end{table}

---

@Mico: I didn't know how to insert a lot of code into the comments, so I answered my own question here. It's just an information table and I want it to look better. The following code has integrated Mico's code.

\documentclass{article}
\usepackage[english]{babel}
\usepackage[letterpaper,top=2cm,bottom=2cm,left=3cm,right=3cm,marginparwidth=1.75cm]{geometry}
\usepackage{amsmath}
\usepackage{graphicx}
\usepackage[colorlinks=true, allcolors=blue]{hyperref}
\usepackage{gensymb}
\usepackage{multirow,tabularx,ragged2e,booktabs,longtable}
\newcolumntype{C}{>{\Centering}X} % centered version of X col. type
\usepackage[skip=0.333\baselineskip]{caption}

\begin{document}

\begin{table}[htbp]
\caption{Fast Hankel Transform} \label{FHT}
\begin{tabularx}{\linewidth}{|*{6}{C|}}
\hline
Order     & Abscissa of $J_0$    & Weight of $J_0$       & Order      & Abscissa of $J_1$    & Weight of $J_1$         \\\hline
1         & $-19.32$             & $9.63\times10^{-7}$   & 1          & $-18.21$             & $-6.77\times10^{-14}$   \\\hline
2         & $-19.11$             & $-5.02\times10^{-6}$  & 2          & $-18.01$             & $3.40\times10^{-13}$    \\\hline
3         & $-18.90$             & $1.25\times10^{-5}$   & 3          & $-17.81$             & $-7.43\times10^{-13}$   \\\hline
$\vdots$  & $\vdots$             & $\vdots$              & $\vdots$   & $\vdots$             & $\vdots$                \\\hline
118       & $5.04$               & $6.23\times10^{-6}$   & 118        & $5.49$               & $7.33\times10^{-6}$     \\\hline
119       & $5.25$               & $-1.12\times10^{-6}$  & 119        & $5.69$               & $-3.76\times10^{-6}$    \\\hline
120       & $5.46$               & $1.04\times10^{-7}$   & 120        & $5.89$               & $1.86\times10^{-6}$     \\\hline
\multicolumn{3}{|c|}             {\multirow{4}{*}{}}     & $\vdots$   & $\vdots$             & $\vdots$                \\
\cline{4-6}    \multicolumn{3}{|c|}{}                    & 138        & $9.54$               & $-1.36\times10^{-9}$    \\
\cline{4-6}    \multicolumn{3}{|c|}{}                    & 139        & $9.74$               & $3.53\times10^{-10}$    \\
\cline{4-6}    \multicolumn{3}{|c|}{}                    & 140        & $9.94$               & $-4.54\times10^{-11}$   \\ \hline
\end{tabularx}
\end{table}
\end{document}

Answer 1

Here are two possible solutions. Both take up the full width of the textblock. The first uses a tabularx environments (with centered versions of the Xcolumn type), and the second uses a tabular*-inspired longtable environment.

The two major differences between the tables is that second (a) gets rid of all vertical lines and most horizontal lines in order to give the table a more open and inviting "look" and (b) allows page breaks, as needed, which may be useful since the real table may have as many as 140 rows.

\documentclass{article}
\usepackage{tabularx,ragged2e,booktabs,longtable}  
\newcolumntype{C}{>{\Centering}X} % centered version of 'X' col. type
\usepackage[skip=0.333\baselineskip]{caption}

\begin{document}

\begin{table}[htbp]
\caption{A ``prison window''-look table} \label{tab:addlabel1}
\begin{tabularx}{\textwidth}{|*{6}{C|}}
    \hline
    order & number & weight & order & number & weight \\
    \hline
    1     & 1     & 1     & 1     & 1     & 1 \\
    \hline
    2     & 2     & 2     & 2     & 2     & 2 \\
    \hline
    3     & 3     & 3     & 3     & 3     & 3 \\
    \hline
    \dots & \dots & \dots & \dots & \dots & \dots \\
    \hline
    118   & 118   & 118   & 118   & 118   & 118 \\
    \hline
    119   & 119   & 119   & 119   & 119   & 119 \\
    \hline
    120   & 120   & 120   & 120   & 120   & 120 \\
    \hline
    &&& \dots & \dots & \dots \\ \cline{4-6}
    &&& 138   & 138   & 138   \\ \cline{4-6}
    &&& 139   & 139   & 139   \\ \cline{4-6}
    &&& 140   & 140   & 140   \\
    \hline
\end{tabularx}
\end{table}


\begingroup % localize scope of next 4 instructions
\setlength\tabcolsep{0pt}
\setlength\LTcapwidth{\textwidth}
\setlength\LTleft{0pt}   % see p. 7 of user guide of longtable package
\setlength\LTright{0pt}
\begin{longtable}{@{\extracolsep{\fill}} *{6}{c} }

    %% information about headers and footers
    
    \caption{A table with a much more open ``look''} \label{tab:addlabel2}\\
    \toprule
    order & number & weight & order & number & weight \\
    \midrule
    \endfirsthead
    
    \multicolumn{6}{l}{\tablename\ \thetable, cont'd}\\
    \addlinespace
    \toprule
    order & number & weight & order & number & weight \\
    \midrule
    \endhead
    
    \midrule
    \multicolumn{6}{r@{}}{\footnotesize \em cont'd on following page}\\
    \endfoot
    
    \bottomrule
    \endlastfoot
    
    %% body of longtable
    
    1     & 1     & 1     & 1     & 1     & 1 \\ 
    2     & 2     & 2     & 2     & 2     & 2 \\
    3     & 3     & 3     & 3     & 3     & 3 \\ 
    $\vdots$ & $\vdots$ & $\vdots$ & $\vdots$ & $\vdots$ & $\vdots$ \\
    118   & 118   & 118   & 118   & 118   & 118 \\
    119   & 119   & 119   & 119   & 119   & 119 \\
    120   & 120   & 120   & 120   & 120   & 120 \\
    &&& $\vdots$ & $\vdots$ & $\vdots$ \\
    &&& 138   & 138   & 138 \\
    &&& 139   & 139   & 139 \\
    &&& 140   & 140   & 140 \\

\end{longtable}
\endgroup

\end{document}

---

Addendum to incorporate additional information provided by the OP: Here's a variant of the tabularx-based solution which (a) allows columns 1 and 4 to be narrower than columns 2, 3, 5, and 6 and (b) allows the numbers in the latter four columns to be aligned on their decimal markers, with the help of the S column type provided by the siunitx package.

\documentclass{article}
\usepackage[english]{babel}
\usepackage[letterpaper,vmargin=2cm,hmargin=3cm,
            marginparwidth=1.75cm]{geometry}
\usepackage{amsmath,graphicx,gensymb}
\usepackage[colorlinks=true, allcolors=blue]{hyperref}

\usepackage{tabularx,ragged2e}
\newcolumntype{C}{>{\Centering}X} % centered version of X col. type
\usepackage[skip=0.333\baselineskip]{caption}
\usepackage{siunitx}
\newcommand\mC[1]{\multicolumn{1}{C|}{#1}} % handy shortcut macro

\begin{document}

\begin{table}[htbp]
\setlength\extrarowheight{2pt} % for a slightly more open "look"
\caption{Fast Hankel Transform} \label{FHT}
\begin{tabularx}{\linewidth}{| *{2}{ c | S[table-format=-2.2] |S[table-format=-1.2e-2]| } }
\hline
Order & \mC{Abscissa of $J_0$} & \mC{Weight of $J_0$} &
Order & \mC{Abscissa of $J_1$} & \mC{Weight of $J_1$} \\
\hline
1         & -19.32   &  9.63e-7  & 1          & -18.21     & -6.77e-14   \\ \hline
2         & -19.11   & -5.02e-6  & 2          & -18.01     &  3.40e-13   \\ \hline
3         & -18.90   &  1.25e-5  & 3          & -17.81     & -7.43e-13   \\ \hline
{$\vdots$} & {$\vdots$} & {$\vdots$} & {$\vdots$} & {$\vdots$} & {$\vdots$} \\ \hline
118       &   5.04   &  6.23e-6  & 118        &   5.49     &  7.33e-6    \\ \hline
119       &   5.25   & -1.12e-6  & 119        &   5.69     & -3.76e-6    \\ \hline
120       &   5.46   &  1.04e-7  & 120        &   5.89     &  1.86e-6    \\ \hline
\multicolumn{3}{|c|}{} & {$\vdots$} & {$\vdots$} & {$\vdots$} \\ \cline{4-6}
\multicolumn{3}{|c|}{} & 138        & 9.54       & -1.36e-9   \\ \cline{4-6}
\multicolumn{3}{|c|}{} & 139        & 9.74       &  3.53e-10  \\ \cline{4-6}
\multicolumn{3}{|c|}{} & 140        & 9.94       & -4.54e-11  \\ \hline
\end{tabularx}
\end{table}

\end{document}