Question: How many years had the best actress in a revival category?
SQL: SELECT COUNT("Year") FROM "2-1715351-1" WHERE "Category" = 'best actress in a revival';

Question: What categories had a Nominated work of Yerma before 1992?
SQL: SELECT "Category" FROM "2-1715351-1" WHERE "Year" < 1992.0 AND "Nominated work" = 'Yerma';