  We develop the method of inducing semiorthogonal decompositions of projective
varieties with isolated rational singularities from those of small resolutions
of singularities, which generalizes semiorthogonal decompositions for singular
surfaces by Karmazyu-Kuznetsov-Shinder.
  \par We first explain the classical generator of the null category, which is
a kind of triangulated full subcategory, and prove that the orthogonal
decompositions of the null category is induced through its generator. Next, we
prove that the candidate of induced semiorthogonal decomposition behaves well
with respect to the inverse image of resolution morphism, and as a corollary,
we obtain the required semiorthogonal decomposition.
