CREATE TABLE table_19753 ("Result" TEXT, "Date" TEXT, "Race" TEXT, "Venue" TEXT, "Group" TEXT, "Distance" TEXT, "Weight  ( kg ) " TEXT, "Jockey" TEXT, "Winner/2nd" TEXT)

How many different jockeys ran on 17 Feb 2007?
SELECT COUNT("Jockey") FROM table_19753 WHERE "Date" = '17 Feb 2007'
SELECT COUNT("Jockey") FROM "table_19753" WHERE "Date" = '17 Feb 2007'