CREATE TABLE table_204_880 (id DECIMAL, "year" DECIMAL, "competition" TEXT, "venue" TEXT, "position" TEXT, "event" TEXT, "notes" TEXT)

how many marathons were held in beijing ?
SELECT COUNT("competition") FROM table_204_880 WHERE "venue" = 'beijing'
SELECT COUNT("competition") FROM "table_204_880" WHERE "venue" = 'beijing'