Table: presidents_rankings
Columns: president
schl_1948
schl_1962
m_b_1982
ct_1982
siena_1982
siena_1990
siena_1994
r_mci_1996
schl_1996
c_span_1999
wsj_2000
siena_2002
wsj_2005
times_2008
c_span_2009
siena_2010
uspc_2011
aggr

Question: Who is the president when c-span 2009 is 21?
SQL: SELECT "president" FROM presidents_rankings WHERE "c_span_2009" = '21'

Question: what is c-span 2009 when times 2008** is 08?
SQL: SELECT "c_span_2009" FROM presidents_rankings WHERE "times_2008" = '08'

Question: what is siena 2002 when the president is andrew jackson?
SQL: SELECT "siena_2002" FROM presidents_rankings WHERE "president" = 'andrew jackson'