CREATE TABLE table_54609 ("Player" TEXT, "Tackles" FLOAT, "Asst." FLOAT, "TotalTK" FLOAT, "Sack" FLOAT, "Yards" FLOAT, "FumR" FLOAT)

what is the sum of totaltk when yards is less than 0?
SELECT SUM("TotalTK") FROM table_54609 WHERE "Yards" < '0'
SELECT SUM("TotalTK") FROM "table_54609" WHERE "Yards" < '0'