  We present a unified explanation for the $B$-decay anomalies in
$R_{D^{(\ast)}}$ and $R_{K}$ together with the anomalous muon magnetic moment,
consistent with the constraints from the current measurements of leptonic decay
rates and $D^0-\bar{D}^0$, $B_{s}^0-\bar{B}_{s}^0$ mixings, within the
framework of a minimal left-right symmetric gauge theory motivated by one of
the low-energy subgroups of $E_{6}$ naturally accommodating leptoquarks.
