代码

\begin{table}
    \caption{Global caption}
    \begin{minipage}{.5\linewidth}
        % \caption{}
        \centering
        \begin{tabular}{ccccc}
            \hline
               & $d_1$ & $d_2$ & $d_3$ & $d_4$ \\
            \hline
            $a_1$ & 0.66 & 0.63 & \textbf{0.95} & 0.65 \\
            $a_2$ & \textbf{0.90} & \textbf{0.81} & 0.89 & \textbf{0.84} \\
            $a_3$ & 0.82 & 0.79 & 0.83 & 0.83 \\
            $a_4$ & 0.74 & 0.76 & 0.84 & 0.77 \\
            \hline
        \end{tabular}
    \end{minipage}
    \begin{minipage}{.5\linewidth}
        \centering
        % \caption{}
        \begin{tabular}{ccccc}
            \hline
               & $d_1$ & $d_2$ & $d_3$ & $d_4$ \\
            \hline
            $a_1$ & 4 & 4 & \textbf{1} & 4 \\
            $a_2$ & \textbf{1} & \textbf{1} & 2 & \textbf{1} \\
            $a_3$ & 2 & 2 & 3 & 2 \\
            $a_4$ & 3 & 3 & 4 & 3 \\
            \hline
        \end{tabular}
    \end{minipage} 
\end{table}

效果

Reference

https://tex.stackexchange.com/questions/2832/how-can-i-have-two-tables-side-by-side