CREATE TABLE table_51028 ("Club" TEXT, "Played" TEXT, "Drawn" TEXT, "Lost" TEXT, "Points for" TEXT, "Points against" TEXT, "Points difference" TEXT, "Bonus Points" TEXT, "Points" TEXT)

What are the points against with a points difference?
SELECT "Points against" FROM table_51028 WHERE "Points difference" = 'points difference'
SELECT "Points against" FROM "table_51028" WHERE "Points difference" = 'points difference'