Question: Among the matches of Delhi Daredevils in 2009, what is the percentage of their matches won by wickets?
SQL: SELECT CAST(SUM(CASE WHEN T3.Win_Type = 'wickets' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(T3.Win_Type) FROM Team AS T1 INNER JOIN Match AS T2 ON T1.Team_Id = T2.Match_Winner INNER JOIN Win_By AS T3 ON T2.Win_Type = T3.Win_Id WHERE T1.Team_Name = 'Delhi Daredevils'