CREATE TABLE table_204_91 (id NUMBER, "year" NUMBER, "original title" CLOB, "english title" CLOB, "role" CLOB, "notes" CLOB)

how many years had passed from malberg 's first film to the first danish film with sound ?
SELECT ((SELECT "year" FROM table_204_91 WHERE "notes" = 'first danish sound film') - (SELECT MIN("year") FROM table_204_91))
SELECT (SELECT "year" FROM "table_204_91" WHERE "notes" = 'first danish sound film') - (SELECT MIN("year") FROM "table_204_91")