CREATE TABLE table_41881 ("Aces" FLOAT, "Player" CLOB, "Opponent" CLOB, "Event" CLOB, "Sets" FLOAT)

At the 2001 Davis Cup, what Opponent had less than 50 Aces?
SELECT "Opponent" FROM table_41881 WHERE "Aces" < '50' AND "Event" = '2001 davis cup'
SELECT "Opponent" FROM "table_41881" WHERE "Aces" < '50' AND "Event" = '2001 davis cup'