For all the set of cards that has Japanese translation, what is the percentage of them are only available in non-foil?
Japanese translation refers to language = 'Japanese'; in non-foil refers to isNonFoilOnly = 1; percentage of Japanese non foil in Japanese cards refers to DIVIDE(SUM(isNonFoilOnly = 1), SUM(language = 'Japanese'))*100
SELECT CAST(SUM(CASE WHEN isNonFoilOnly = 1 THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(id) FROM sets WHERE code IN ( SELECT setCode FROM set_translations WHERE language = 'Japanese' )