LaTeX: tabular environments act as groups

gistfile1

\documentclass{article}

\begin{document}
\newlength{\myl}

Q
\settoheight{\myl}{Q}
height=\the\myl
\settodepth{\myl}{Q}
depth=\the\myl
\settowidth{\myl}{Q}
width=\the\myl

\begin{table}[h]
\begin{tabular}{ll}
\settoheight{\myl}{Q} height &\the\myl \\
\settodepth{\myl}{Q}  depth  &\the\myl \\
\settowidth{\myl}{Q}  width  &\the\myl \\
\end{tabular}
\end{table}
\end{document}