CREATE TABLE table_203_549 (id DECIMAL, "player" TEXT, "team" TEXT, "date" TEXT, "opponent" TEXT, "venue" TEXT)

which teams faced off at miller park ?
SELECT "team" FROM table_203_549 WHERE "venue" = 'miller park' UNION SELECT "opponent" FROM table_203_549 WHERE "venue" = 'miller park'
SELECT "team" FROM "table_203_549" WHERE "venue" = 'miller park' UNION SELECT "opponent" FROM "table_203_549" WHERE "venue" = 'miller park'