Table: xfactor_au
Columns: series
start
finish
winner
runner_up
third_place
winning_mentor
main_host

Question: What is the start date with Luke Jacobz hosting and Dannii Minogue as a winning mentor?
SQL: SELECT "start" FROM xfactor_au WHERE "main_host" = 'luke jacobz' AND "winning_mentor" = 'dannii minogue'

Question: Who was in third place when Guy Sebastian was the winning mentor and Andrew Wishart was the runner-up?
SQL: SELECT "third_place" FROM xfactor_au WHERE "winning_mentor" = 'guy sebastian' AND "runner_up" = 'andrew wishart'