Table: world_vball_2009
Columns: date
score
set_1
set_2
total

Question: What is the score for Set 2 at 15:21?
SQL: SELECT "score" FROM world_vball_2009 WHERE "set_2" = '15:21'

Question: What Set 2 has a set one at 19:21?
SQL: SELECT "set_2" FROM world_vball_2009 WHERE "set_1" = '19:21'

Question: What is the score for Set 1 at 19:21?
SQL: SELECT "score" FROM world_vball_2009 WHERE "set_1" = '19:21'

Question: What is the Set 1 with set 2 at 21:17?
SQL: SELECT "set_1" FROM world_vball_2009 WHERE "set_2" = '21:17'