  We compiled the radio, optical, and X-ray data of blazars from the Sloan
Digital Sky Survey (SDSS) database, and presented the distribution of
luminosities and broad band spectral indices. The distribution of luminosities
shows that the averaged luminosity of flat-spectral radio quasars (FSRQs) is
larger than that of BL Lacs objects. On the other hand, the broad band spectral
energy distribution reveals that FSRQs and low energy peaked BL Lac objects
(LBLs) objects have similar spectral properties, but high energy peaked BL Lac
objects (HBLs) have a distinct spectral property. This may be due to that
different subclasses of blazars have different intrinsic environments and are
at different cooling levels. Even so, a unified scheme also is revealed from
the color-color diagram, which hints that there are similar physical processes
operating in all objects under a range of intrinsic physical conditions or
beaming parameter.
