What is the percentage of the teams who had post season (playoff) were ranked number 1?
had post season (play off) refers to playoff is not null; percentage = Divide (Count(Team where rank = 1, Count(Team))) * 100
SELECT CAST(SUM(CASE WHEN rank = 1 THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(name) FROM teams