  We aim to reveal the nature of the Sloan Digital Sky Survey (SDSS) stars:
SDSSJ100921.40+375233.9, SDSSJ015717.04+135535.9, and SDSSJ171422.43+283657.2,
showing apparently high NUV excesses for their g-z colors, as expected for
extremely low-metallicity stars. High resolution (R=60 000) spectra of the
stars with a wide wavelength coverage were obtained to determine their chemical
compositions with the Tull echelle spectrograph on the 2.7 m telescope at the
McDonald Observatory. We derived the spectroscopic parameters Teff =5820+-125
K, log g =3.9+-0.2, and vt =1.1+-0.5 km/s for SDSSJ100921.40+375233.9,
Teff=6250+-125 K, log g =3.7+-0.2, and vt =4.0+-0.5 km/s for
SDSSJ015717.04+135535.9, and Teff=6320+-125 K, log g =4.1+-0.3, and vt
=1.5+-0.5 km/s for SDSS J171422.43+283657.2, and elemental abundances were
computed for 21 elements for J100921 and J171422 and for 19 elements for
J015717 for the first time. We find metallicities of [Fe/H]= -1.30, -0.94, and
-0.80 for SDSSJ100921.40+375233.9, J015717.04+135535.9, and
J171422.43+283657.2, respectively. On the basis of calculated abundance ratios
for J171422.43+283657.2 and J015717.04+135535.9, we also report that these two
program stars have the expected composition of main-sequence halo turnoff
stars, but with low-alpha abundances, i.e., the [alpha/Fe] ratio is ~0.0 for
J171422.43+283657.2 and ~0.1 for J015717.04+135535.9. The latter one shows
typical halo or thick-disk alpha-element abundances, but has a substantial
rotational line broadening and vsini=40 +- 0.5 km/s.
