CREATE TABLE table_26919 ("Round" FLOAT, "Circuit" CLOB, "Date" CLOB, "Pole Position" CLOB, "Fastest Lap" CLOB, "Winning Rider" CLOB, "Winning Team" CLOB)

How many dates was knockhill?
SELECT COUNT("Date") FROM table_26919 WHERE "Circuit" = 'Knockhill'
SELECT COUNT("Date") FROM "table_26919" WHERE "Circuit" = 'Knockhill'