CREATE TABLE table_51917 ("Home team" TEXT, "Home team score" TEXT, "Away team" TEXT, "Away team score" TEXT, "Venue" TEXT, "Crowd" FLOAT, "Date" TEXT)

What is the highest crowd with north melbourne as away team?
SELECT MAX("Crowd") FROM table_51917 WHERE "Away team" = 'north melbourne'
SELECT MAX("Crowd") FROM "table_51917" WHERE "Away team" = 'north melbourne'