CREATE TABLE table_name_31 (season INT, team_2 VARCHAR, team_1 VARCHAR, score VARCHAR)

What year did Bangkok University and Chunnam Dragons have a score of 0-0?
SELECT SUM(season) FROM table_name_31 WHERE team_1 = "bangkok university" AND score = "0-0" AND team_2 = "chunnam dragons"
SELECT SUM("season") FROM "table_name_31" WHERE "0-0" = "score" AND "bangkok university" = "team_1" AND "chunnam dragons" = "team_2"