\documentclass{article}
\usepackage{rotating}

\begin{document}

Example of a sideways table:

\begin{table}[ht]
\caption{\small Results for Datasets~\#1 and 2.}
\begin{sideways}
\begin{small}
\begin{tabular}{|c||c|c|c|c||c|c|c|c||c|c|c|c||c|}\hline
\multicolumn{13}{|c|}{Dataset~\#1, Improvement measurements} & \\\hline
$t$ & \multicolumn{4}{c||}{Time } &  \multicolumn{4}{c||}{\#NV} &  \multicolumn{4}{c|}{\#CC} & FBS \\\cline{2-13}
& \multicolumn{3}{|c|}{t-distribution}&F-value&  \multicolumn{3}{|c|}{t-distribution} & F-value & \multicolumn{3}{|c|}{t-distribution} & F-value &  \\
& UL & Mean & LL &  &  UL & Mean & LL &  &  UL & Mean & LL &  & \\\hline\hline
0.4000&-25.86&-42.59&-61.53&63.86&23.01&12.91&1.49&11.94&22.13&11.83&0.18&8.13&263.4\\
0.4750&19.41&8.70&-3.43&4.20&28.83&19.50&8.94&26.44&27.14&17.51&6.60&18.98&48.46\\\cline{1-1}
\multicolumn{1}{||c||}{0.5500}&44.12&31.93&17.09&30.03&43.27&31.07&16.23&30.77&42.06&29.49&14.2&25.03&1.07\\
\multicolumn{1}{||c||}{0.5750}&34.70&26.03&16.20&46.10&34.27&25.65&15.89&47.65&33.64&24.87&14.94&41.89&0.30\\\cline{1-1}
0.7000&34.88&26.23&16.43&46.95&28.14&18.72&8.05&24.32&29.55&20.24&9.70&26.22&0.00\\\hline
 \multicolumn{13}{c}{}\\\hline
\multicolumn{13}{|c}{Dataset~\#2, Improvement measurements} & \\\hline
$t$ & \multicolumn{4}{c||}{Time } &  \multicolumn{4}{c||}{\#NV} &  \multicolumn{4}{c|}{\#CC} & FBS \\\cline{2-13}
& \multicolumn{3}{|c|}{t-distribution}&F-value&  \multicolumn{3}{|c|}{t-distribution} & F-value & \multicolumn{3}{|c|}{t-distribution} & F-value &  \\
& UL & Mean & LL &  &  UL & Mean & LL &  &  UL & Mean & LL &  & \\\hline\hline
0.3500&-67.6&-92.62&-121.38&175.23&24.84&10.29&-7.06&4.98&22.39&10.15&-4.03&4.21&111.35\\
0.4625&13.56&0.65&-14.18&0.02&29.35&15.68&0.01&9.34&26.04&14.37&0.86&8.85&9.71\\\cline{1-1}
\multicolumn{1}{||c||}{0.4875}&27.85&17.08&4.70&14.3&31.3&18.01&2.14&11.95&28.34&17.04&3.94&12.83&4.57\\
\multicolumn{1}{||c||}{0.5375}&34.4&24.61&13.36&32.58&33.94&21.17&5.92&16.29&31.45&20.64&8.12&19.67&0.13\\\cline{1-1}
0.6000&36.53&28.61&19.69&64.81&37.38&27.28&15.55&37.86&34.67&26.06&16.31&46.93&0.00\\\hline
\end{tabular}
\end{small}
\end{sideways}
\label{tab:set1-2}
\end{table}

\end{document}