URL: http://cas.sdss.org/dr12/en/tools/search/sql.aspx
SQL:

SELECT p.ra,p.dec,s.z as redshift
FROM PhotoObj AS p
   JOIN SpecObj AS s ON s.bestobjid = p.objid
WHERE 
   p.u BETWEEN 0 AND 19.6
   AND g BETWEEN 0 AND 20
