Issue in using longtable within table environment

Question

I have an issue making a long list with wrapped text. The table can be several page long. I use longtable and assign the width for each column but as soon as I put it in the \begin{table} \end{table}, it does not work. It clips the table. I want to make a label for the table so I put it in the table environment.

And is there a way to automatically adjust the width so that I don't need to assign the value manually?

Thank you.

Tung

\begin{table}
\centering
\begin{longtable}{|p{6.5cm}|p{2.5cm}|p{2.5cm}|p{2.5cm}|}
\hline
Name                                      & Company     &  Catalog Number   &   Comments    \\ \hline
Small DNA FRAG Extract Kit-100PR          & VWR         &   97060-558 & \\ \hline
Acrylamide 40\% solution 500 mL           & VWR         &   97064-522 &  \\ \hline
Bis-acrylamide 2\% (w/v) solution 500 mL  & VWR         &   97063-948 &  \\ \hline
GeneRuler 100 bp DNA Ladder, 100-1,000 bp & Fermentas   &   SM0241  &    \\ \hline
Mini Vertical PAGE System                 & VWR         &   89032-300  &  \\ \hline
\end{longtable}
\label{tab:list}
\end{table}

Answer 1

table encloses its contents in a box which will not break across pages, but which can "float" to a convenient location. longtable gets rid of this box, is able to break across pages, and does not float. Hence enclosing longtable inside a table defeats the entire purpose. Remove table environment.

longtable provides a \caption facility and hence you can add a \label too.

A sample

\documentclass{article}
\usepackage{longtable}
\begin{document}
\begin{longtable}{|p{6.5cm}|p{2.5cm}|p{2.5cm}|p{2.5cm}|}
\caption[An optional table caption]{A long table\label{tab:list}}\\
\hline
Name                                      & Company     &  Catalog Number   &   Comments    \\ \hline
Small DNA FRAG Extract Kit-100PR          & VWR         &   97060-558 & \\ \hline
Acrylamide 40\% solution 500 mL           & VWR         &   97064-522 &  \\ \hline
Bis-acrylamide 2\% (w/v) solution 500 mL  & VWR         &   97063-948 &  \\ \hline
GeneRuler 100 bp DNA Ladder, 100-1,000 bp & Fermentas   &   SM0241  &    \\ \hline
Mini Vertical PAGE System                 & VWR         &   89032-300  &  \\ \hline
\end{longtable}

A long table~\ref{tab:list} is here.

\end{document}

For more details read the longtable documentation (available if you run texdoc longtable from command prompt/terminal or from your tex editor's help menu.

Here is an improved version with better widths

\documentclass{article}
\usepackage{longtable,array,showframe}   %% Remove showframe
\begin{document}
\begin{longtable}{|>{\raggedright}m{0.4\textwidth}|
                   >{\raggedright}p{0.13\textwidth}|
                   >{\raggedright}p{0.15\textwidth}|
                   >{\raggedright\arraybackslash}p{0.13\textwidth}|}
\caption[An optional table caption]{A long table\label{tab:list}}\\
\hline
Name                                      & Company     &  Catalog Number   &   Comments    \\ \hline
Small DNA FRAG Extract Kit-100PR          & VWR         &   97060-558 & \\ \hline
Acrylamide 40\% solution 500 mL           & VWR         &   97064-522 &  \\ \hline
Bis-acrylamide 2\% (w/v) solution 500 mL  & VWR         &   97063-948 &  \\ \hline
GeneRuler 100 bp DNA Ladder, 100-1,000 bp & Fermentas   &   SM0241  &    \\ \hline
Mini Vertical PAGE System                 & VWR         &   89032-300  &  \\ \hline
\end{longtable}

A long table~\ref{tab:list} is here.

\end{document}

And this is obligatory booktabs version:

\documentclass{article}
\usepackage{longtable,array,booktabs,showframe}
\begin{document}
\begin{longtable}{>{\raggedright}m{0.4\textwidth}
                   >{\raggedright}p{0.13\textwidth}
                   >{\raggedright}p{0.15\textwidth}
                   >{\raggedright\arraybackslash}p{0.13\textwidth}}
\caption[An optional table caption]{A long table\label{tab:list}}\\
\toprule
Name                                      & Company     &  Catalog Number   &   Comments    \\ \midrule
Small DNA FRAG Extract Kit-100PR          & VWR         &   97060-558 & \\ 
Acrylamide 40\% solution 500 mL           & VWR         &   97064-522 &  \\ 
Bis-acrylamide 2\% (w/v) solution 500 mL  & VWR         &   97063-948 &  \\ 
GeneRuler 100 bp DNA Ladder, 100-1,000 bp & Fermentas   &   SM0241  &    \\ 
Mini Vertical PAGE System                 & VWR         &   89032-300  &  \\ \bottomrule
\end{longtable}

A long table~\ref{tab:list} is here.

\end{document}

Answer 2

As an aside, one routinely also reduces table font sizes to ensure that they fit within the page width for table environments. Though longtable supports captions, it will ignore font size commands, such as \tiny and \scriptsize. However, the longtable itself can be wrapped within a font size environment, thus ensuring desired output.

\begin{scriptsize}
    \begin{longtabu} to \textwidth {rllrrll}
        \caption[Largest cities by highest reduction target]{Each country's largest city, its location, and each countries highest promised reduction target.} \\
        \toprule
        \rowfont\bfseries & Country & Largest City & Latitude & Longitude & Highest   & Notes \\
        \rowfont\bfseries &         &              &          &           & Reduction & \\
        \rowfont\bfseries &         &              &          &           & Target    & \\ \midrule
        \endhead

        \\ \hline 
        \multicolumn{7}{r}{Continued on next page} \\
        \endfoot

        \bottomrule
        \endlastfoot

        1 & Cape Verde & Praia & 14.92 & -23.51 & 100\% & electricity sector \\ 
        2 & Papua New Guinea & Port Moresby & -9.48 & 147.15 & 100\% & for electricity generation \\ 
    \end{longtabu}
\end{scriptsize}