Fancy Labels for Tables

Question

I am trying to draw relational database tables with tabular. I would like to label each table with a label at the top left of the table. Neither solution that comes to my mind is exactly what I want.

I would like a rectangular label with the following properties:

• Border width is same as that of table
• Left border aligns with left border of table
• Bottom border overlaps top border of table
• Width is less than column width of table

In the first solution, I use Tikz and try to draw the label as a rectangular node. I can never quite get the bottom border of the label to overlap the top border of the table. Nor can I get the left border to align with that of the table.

In the second solution, I use multicolumn. This comes very close, the only problem remaining is the width.

\documentclass[a4paper]{article}

\usepackage{tikz}
\usetikzlibrary{calc, positioning}

\begin{document}

\begin{tikzpicture}

\node (A) {
\begin{tabular}{|l|l|l|||l|}
\hline
$\texttt{o\_orderkey}$ & $\texttt{o\_orderdate}$ & $\texttt{o\_custkey}$ & rest \\
\hline
0 & 1992-01-01   & 100 & A \\
1 & 1992-01-15   & 3 & B \\ 
200 & 1993-01-01 & 26 & C \\
201 & 1993-01-15 & 42 & D \\
300 & 1994-01-01 & 88 & E \\
301 & 1994-01-01 & 74 & F \\
\hline
\end{tabular}
};

\node[draw, anchor=south west, inner sep=2pt] at (A.north west) {Table};

\end{tikzpicture}

\begin{tabular}{|l|l|l|||l|}
\cline{1-1} \multicolumn{1}{|l|}{Label} \\
\hline
$\texttt{o\_orderkey}$ & $\texttt{o\_orderdate}$ & $\texttt{o\_custkey}$ & rest \\
\hline
0 & 1992-01-01   & 100 & A \\
1 & 1992-01-15   & 3 & B \\ 
200 & 1993-01-01 & 26 & C \\
201 & 1993-01-15 & 42 & D \\
300 & 1994-01-01 & 88 & E \\
301 & 1994-01-01 & 74 & F \\
\hline
\end{tabular}

\end{document}

Answer 1

You can box the label and adjust it so that the bottom rule overlaps the first \hline.

\documentclass[a4paper]{article}

\newcommand{\tablelabel}[1]{%
  \multicolumn{1}{@{}l@{}}{%
    \setlength{\fboxsep}{0pt}%
    \setlength{\fboxrule}{\arrayrulewidth}%
    \hspace{-.5\arrayrulewidth}%
    \fbox{\hspace{\tabcolsep}\strut#1\hspace{\tabcolsep}}%
  }\\[-\arrayrulewidth]
}

\begin{document}

\begin{tabular}{|l|l|l|l|}
\tablelabel{Label}
\hline
\texttt{o\_orderkey} & \texttt{o\_orderdate} & \texttt{o\_custkey} & rest \\
\hline
  0 & 1992-01-01 & 100 & A \\
  1 & 1992-01-15 &   3 & B \\ 
200 & 1993-01-01 &  26 & C \\
201 & 1993-01-15 &  42 & D \\
300 & 1994-01-01 &  88 & E \\
301 & 1994-01-01 &  74 & F \\
\hline
\end{tabular}

\end{document}

Note that you don't need $...$ around \texttt.

You may want a slightly different version that allows for specifying the number of columns to be spanned, in case the label is wider than the first column.

\documentclass[a4paper]{article}
\usepackage{xparse}

\DeclareExpandableDocumentCommand{\tablelabel}{O{1}m}{%
  \multicolumn{#1}{@{}l@{}}{%
    \setlength{\fboxsep}{0pt}%
    \setlength{\fboxrule}{\arrayrulewidth}%
    \hspace{-.5\arrayrulewidth}%
    \fbox{\hspace{\tabcolsep}\strut#2\hspace{\tabcolsep}}%
  }\\[-\arrayrulewidth]
}

\begin{document}

\begin{tabular}{|l|l|l|l|}
\tablelabel[4]{Label}
\hline
\texttt{o\_orderkey} & \texttt{o\_orderdate} & \texttt{o\_custkey} & rest \\
\hline
  0 & 1992-01-01 & 100 & A \\
  1 & 1992-01-15 &   3 & B \\ 
200 & 1993-01-01 &  26 & C \\
201 & 1993-01-15 &  42 & D \\
300 & 1994-01-01 &  88 & E \\
301 & 1994-01-01 &  74 & F \\
\hline
\end{tabular}

\end{document}

The [4] optional argument in the example is not really necessary, but is used just to show the syntax.

In case you decide to use booktabs and avoid vertical rules, which I recommend, a simple modification is needed (no backspace of half the \arrayrulewidth).

\documentclass[a4paper]{article}
\usepackage{booktabs,xparse}

\DeclareExpandableDocumentCommand{\tablelabel}{O{1}m}{%
  \multicolumn{#1}{@{}l@{}}{%
    \setlength{\fboxsep}{0pt}%
    \setlength{\fboxrule}{\arrayrulewidth}%
    \fbox{\hspace{\tabcolsep}\strut#2\hspace{\tabcolsep}}%
  }\\[-\arrayrulewidth]
}

\begin{document}

\begin{tabular}{llll}
\tablelabel[4]{Label}
\toprule
\texttt{o\_orderkey} & \texttt{o\_orderdate} & \texttt{o\_custkey} & rest \\
\midrule
  0 & 1992-01-01 & 100 & A \\
  1 & 1992-01-15 &   3 & B \\ 
200 & 1993-01-01 &  26 & C \\
201 & 1993-01-15 &  42 & D \\
300 & 1994-01-01 &  88 & E \\
301 & 1994-01-01 &  74 & F \\
\bottomrule
\end{tabular}

\end{document}

Answer 2

Is it like this?

\documentclass[a4paper]{article}

\usepackage{tikz}
\usetikzlibrary{calc, positioning}

\begin{document}

\begin{tikzpicture}

\node[anchor=north west,inner sep=0pt,outer sep=0pt] (A) {
\begin{tabular}{|l|l|l|||l|}
\hline
$\texttt{o\_orderkey}$ & $\texttt{o\_orderdate}$ & $\texttt{o\_custkey}$ & rest \\
\hline
0 & 1992-01-01   & 100 & A \\
1 & 1992-01-15   & 3 & B \\
200 & 1993-01-01 & 26 & C \\
201 & 1993-01-15 & 42 & D \\
300 & 1994-01-01 & 88 & E \\
301 & 1994-01-01 & 74 & F \\
\hline
\end{tabular}
};

\node[draw, anchor=south west,text depth=0.5ex, inner ysep=2pt,inner xsep=\tabcolsep,outer sep=0pt] at ([yshift=-0.5\pgflinewidth]A.north west) {Table};

\end{tikzpicture}

\begin{tabular}{|l|l|l|l|||l|}
\cline{1-1} Label \\
\hline
\multicolumn{2}{|l|}{$\texttt{o\_orderkey}$} & $\texttt{o\_orderdate}$ & $\texttt{o\_custkey}$ & rest \\
\hline
\multicolumn{2}{|l|}{0} & 1992-01-01   & 100 & A \\
\multicolumn{2}{|l|}{1} & 1992-01-15   & 3 & B \\
\multicolumn{2}{|l|}{200} & 1993-01-01 & 26 & C \\
\multicolumn{2}{|l|}{201} & 1993-01-15 & 42 & D \\
\multicolumn{2}{|l|}{300} & 1994-01-01 & 88 & E \\
\multicolumn{2}{|l|}{301} & 1994-01-01 & 74 & F \\
\hline
\end{tabular}

\end{document}

Answer 3

A very simple solution, using the caption package:

\documentclass[a4paper]{article}
\usepackage{amsmath}
\usepackage{caption}
\DeclareCaptionFormat{mine}{\setlength\fboxsep{0pt}\hskip-0.5\arrayrulewidth\fbox{\space#3\space}}

\begin{document}

\begin{table}
\captionsetup{singlelinecheck = false, format = mine, skip =-\arrayrulewidth}
 \caption{Label}
\begin{tabular}{|l|l|l|||l|}
\hline
\texttt{o\_orderkey} & \texttt{o\_orderdate} & \texttt{o\_custkey} & rest \\
\hline
0 & 1992-01-01   & 100 & A \\
1 & 1992-01-15   & 3 & B \\
200 & 1993-01-01 & 26 & C \\
201 & 1993-01-15 & 42 & D \\
300 & 1994-01-01 & 88 & E \\
301 & 1994-01-01 & 74 & F \\
\hline
\end{tabular}
\end{table}

\end{document} 

Answer 4

Here is a solution with {NiceTabular} of nicematrix.

That environment is similar to the classical {tabular} (of the package array) but creates PGF/Tikz nodes under the cells, rows and columns. You can use these with Tikz to draw whatever rule you want.

\documentclass[a4paper]{article}
\usepackage{nicematrix,tikz}

\begin{document}

\begin{NiceTabular}{llll}
  table \\
  \hline
  \Block[vlines]{*-*}{}
  \verb|o_orderkey| & \verb|o_orderdate| & \verb|o_custkey| & rest \\
  \hline
  0   & 1992-01-01 & 100 & A \\
  1   & 1992-01-15 & 3   & B \\
  200 & 1993-01-01 & 26  & C \\
  201 & 1993-01-15 & 42  & D \\
  300 & 1994-01-01 & 88  & E \\
  301 & 1994-01-01 & 74  & F \\
  \hline
\CodeAfter 
  \tikz \draw (1-|1) -| ([xshift=\tabcolsep]1-1.east) |- (2-|1) -- cycle ; 
\end{NiceTabular}

\end{document}

You need several compilations (because nicematrix uses PGF/Tikz nodes under the hood).