CREATE TABLE table_18143210_2 (first_season_in_top_division VARCHAR2, club VARCHAR2)

When did the club UNAM played the first season in top division?
SELECT first_season_in_top_division FROM table_18143210_2 WHERE club = "UNAM"
SELECT "first_season_in_top_division" FROM "table_18143210_2" WHERE "UNAM" = "club"