CREATE TABLE table_204_455 (id NUMBER, "rd." NUMBER, "grand prix" CLOB, "date" CLOB, "location" CLOB, "pole position" CLOB, "fastest lap" CLOB, "winning driver" CLOB, "constructor" CLOB, "report" CLOB)

what grand prix was before the san marino grand prix ?
SELECT "grand prix" FROM table_204_455 WHERE "rd." = (SELECT "rd." FROM table_204_455 WHERE "grand prix" = 'san marino grand prix') - 1
SELECT "grand prix" FROM "table_204_455" WHERE "rd." = (SELECT "rd." FROM "table_204_455" WHERE "grand prix" = 'san marino grand prix') - 1