CREATE TABLE table_203_244 (id DECIMAL, "pos" TEXT, "rider" TEXT, "manufacturer" TEXT, "time/retired" TEXT, "points" DECIMAL)

how many total riders rode a yamaha bike ?
SELECT COUNT("rider") FROM table_203_244 WHERE "manufacturer" = 'yamaha'
SELECT COUNT("rider") FROM "table_203_244" WHERE "manufacturer" = 'yamaha'