CREATE TABLE table_204_510 (id DECIMAL, "team 1" TEXT, "agg." TEXT, "team 2" TEXT, "1st leg" TEXT, "2nd leg" TEXT)

what nation is next after porto on team 2
SELECT "team 2" FROM table_204_510 WHERE id = (SELECT id FROM table_204_510 WHERE "team 2" = 'porto') + 1
SELECT "team 2" FROM "table_204_510" WHERE "id" = (SELECT "id" FROM "table_204_510" WHERE "team 2" = 'porto') + 1