Table: breeders_cup_marathon
Columns: year
winner
jockey
trainer
owner
time
purse

Question: What was the purse when the trainer was Aidan O'Brien?
SQL: SELECT "purse" FROM breeders_cup_marathon WHERE "trainer" = 'aidan o''brien'

Question: What is the time for when cornelio velasquez was the jockey?
SQL: SELECT "time" FROM breeders_cup_marathon WHERE "jockey" = 'cornelio velasquez'

Question: Who was the jockey when the owner was Richard Pegum?
SQL: SELECT "jockey" FROM breeders_cup_marathon WHERE "owner" = 'richard pegum'

Question: What is the purse when Aidan O'brien was the trainer?
SQL: SELECT "purse" FROM breeders_cup_marathon WHERE "trainer" = 'aidan o''brien'

Question: What is the purse for the year earlier than 2013 and muhannak was the winner?
SQL: SELECT "purse" FROM breeders_cup_marathon WHERE "year" < 2013 AND "winner" = 'muhannak'

Question: Who was the trainer in 2013?
SQL: SELECT "trainer" FROM breeders_cup_marathon WHERE "year" = 2013