Calculate the win rate of the team "Chennai Super Kings".
team "Chennai Super Kings" refers to Team_Name = 'Chennai Super Kings'; win rate = divide(count(Match_Id where Match_Winner = 3), count(Match_Id)) * 100%
SELECT CAST(SUM(CASE WHEN T1.Match_Winner = 3 THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(T1.Match_Id) FROM Match AS T1 INNER JOIN Team AS T2 ON T2.Team_Id = T1.Team_1 INNER JOIN Team AS T3 ON T3.Team_Id = T1.Team_2 WHERE T2.Team_Name = 'Chennai Super Kings' OR T3.Team_Name = 'Chennai Super Kings'