I need to draw a double line after the first row in a table, but when using \hline twice, this interrupts the vertical lines:
\documentclass{article}
\begin{document}
\begin{tabular}{|c|c|c|}
\hline
1 & 2 & 3 \\ \hline \hline
4 & 5 & 6 \\ \hline
7 & 8 & 9 \\ \hline
\end{tabular}
\end{document}
produces:

This is without using any additional packages. How can I change this is such a ways that the vertical lines are not interrupted?


1 & 2 & 3 \\ \hhline{}but then the horizontal line just disappears. I also tried1 & 2 & 3 \\ \hhline{===}but then the vertical lines were still interrupted. If not that, what is the proper argument for this function? – Jelle Aug 30 '13 at 14:241 & 2 & 3 \\ \hhline{|=|=|=|}– karlkoeller Aug 30 '13 at 14:28