\documentclass{article}

\usepackage{filecontents}
\begin{filecontents*}{testbase.csv}
myfoo,mybar,myfoobar
17,barbar,bar 1
,,bar 234
,,barbary
23,ba ba ba,\(a^2+b^2=c^2\)
,,\emph{barfoo}
,,foofoofoo
\end{filecontents*}

\usepackage{etoolbox}
\usepackage{tabu}
\usepackage{longtable}
\usepackage{datatool}

\DTLloaddb[keys={foo,bar,foobar}]{mydatabase}{testbase.csv}

\newcommand{\printcommand}[2][]{%
  \begin{longtabu}to\textwidth{@{}llX@{}}
    \firsthline
    Foo & Bar & Foobar \\
    \hline\endhead
    \DTLforeach*{#2}{\foo=foo,\bar=bar,\foobar=foobar}{%
      \DTLiffirstrow{}{\ifdefempty{\bar}{\\}{\\\hline}}%
      \foo & \bar & \foobar
    } \\ \hline
  \end{longtabu}
}

\begin{document}

foobar

\printcommand{mydatabase}

\end{document}