[Tex/LaTex] How to do a table with top corner removed

tables

I want to do a table with some columns (9) but I want the first 2 columns on the first row to be empty. I can't seem to be able to close the top of my table the way I do it.

\begin{tabular}{|c|c||c|c|c||c|c|c||c|}
\multicolumn{2}{c||}{}&\multicolumn{3}{c||}{Dimensions finies}&\multicolumn{3}{|c||}{   Dimensions brutes}\\
\hline
Identification & Qté & Long.&Larg.& Épais.& Long.& Larg.& Épais. &PMP\\
\hline
Dessus & $1$ & $46$ & $28$ & $6/4$& & & & \\
\hline
Pattes & $4$ & $37\sfrac{1}{2}$ & $3$ & $2$& & & & \\
\hline
\end{tabular}

Best Answer

You can use \cline{i-j} to draw a line from column i to column j; however, I would like to suggest you the booktabs package to design your tables; your table with and without booktabs:

\documentclass{article}
\usepackage{booktabs}
\usepackage{array}

\begin{document}

\noindent\begin{tabular}{*{9}{|c}|}
\cline{3-8}
\multicolumn{2}{c}{}&\multicolumn{3}{||c||}{Dimensions finies}&\multicolumn{3}{|c||}{   Dimensions brutes}\\
\hline
Identification & Qté & Long.&Larg.& Épais.& Long.& Larg.& Épais. &PMP\\
\hline
Dessus & $1$ & $46$ & $28$ & $6/4$& & & & \\
\hline
Pattes & $4$ & $37\frac{1}{2}$ & $3$ & $2$& & & & \\
\hline
\end{tabular}

\vspace{20pt}

\noindent\begin{tabular}{@{}c*{7}{c}c@{}}
\toprule
& &\multicolumn{3}{c}{Dimensions finies}&\multicolumn{3}{c}{Dimensions brutes}\\
\cmidrule(r){1-2}\cmidrule(lr){3-5}\cmidrule(lr){6-8}\cmidrule(l){9-9}
Identification & Qté & Long.&Larg.& Épais.& Long.& Larg.& Épais. &PMP\\
\cmidrule(r){1-1}\cmidrule(lr){2-2}\cmidrule(lr){3-3}
\cmidrule(lr){4-4}\cmidrule(lr){5-5}\cmidrule(lr){6-6}
\cmidrule(lr){7-7}\cmidrule(lr){8-8}\cmidrule(l){9-9}
Dessus & $1$ & $46$ & $28$ & $6/4$& & & & \\
\midrule
Pattes & $4$ & $37\frac{1}{2}$ & $3$ & $2$& & & & \\
\bottomrule
\end{tabular}

\end{document}

enter image description here

As you can see, there's really no need for the vertical rules and the table now looks much better than before.

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