What is the percentage of Japanese cars in the database?
Japanese car refers to country = 'Japan'; percentage = divide(count(ID where country = 'Japan'), count(ID)) * 100%
SELECT CAST(SUM(CASE WHEN T2.country = 'Japan' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(*) FROM production AS T1 INNER JOIN country AS T2 ON T1.country = T2.origin
database name:db_id cars
country table country Cols: origin dtype integer, country dtype text, 
price table price Cols: ID dtype integer, price dtype real, 
data table data Cols: ID dtype integer, mileage per gallon dtype real, number of cylinders dtype integer, displacement dtype real, horse power dtype integer, weight dtype integer, acceleration dtype real, model dtype integer, car name dtype text, 
production table production Cols: ID dtype integer, model year dtype integer, country dtype integer, 
