CREATE TABLE table_203_839 (id DECIMAL, "station" TEXT, "type" TEXT, "latitude" TEXT, "longitude" TEXT, "el.  ( m ) " DECIMAL, "opened" DECIMAL, "closed" DECIMAL, "coordinates" TEXT)

the first opened station
SELECT "station" FROM table_203_839 ORDER BY "opened" LIMIT 1
SELECT "station" FROM "table_203_839" ORDER BY "opened" NULLS FIRST LIMIT 1