我正在使用oracle编写查询以获取每年每种电影编号的类型，但是遇到两个问题：
如果我想添加一个名为before2015的新列，以汇总每种类型在2015年之前制作的电影数量，该怎么办？ 我已经尝试过解码，但是似乎只能识别像2015这样的实际单词，而不是表达式<2015
在以下类型中，如果我想将所有经典类型组合成一排，则科幻经典电影有很多类型，而不是经典，经典戏剧，经典浪漫，经典战争。我该如何实现？
SQL> select decode(genre,null,'Year Total',genre) genre,
2 sum(decode (year, 2015, 1, 0)) Year2015,
3 sum(decode (year, 2016, 1, 0)) Year2016,
4 sum(decode (year, 2017, 1, 0)) Year2017
5 from film
6 group by rollup(genre);
GENRE YEAR2015 YEAR2016 YEAR2017
------------------------- ---------- ---------- ----------
Action and Adventure 1 1 0
Children and Family 0 1 1
Classic 0 0 0
Classic, Drama 0 0 0
Classic, Romance 0 0 0
Classic, War 0 0 0
Comedy 0 0 0
Documentary 0 0 0
Fantasy 1 0 0
Sci-Fi 0 2 1
TV Drama 2 0 1
TV Sci-Fi 0 0 0
Thriller 0 0 0
War 0 0 0
Year Total 4 4 3
编辑 这是示例数据：
INSERT INTO film VALUES ('11W', 'Wide Screen', 'Gone with the Wind', 1939, 2, null, 233, 'Romance');
INSERT INTO film VALUES ('12F', 'Full Screen', 'The Longest Day', 1962, 1, null, 178, 'War');
INSERT INTO film VALUES ('13F', 'Full Screen', 'Roman Holiday', 1953, 1, 'NR', 118, 'Classic');
INSERT INTO film VALUES ('14F', 'Full Screen', 'Sabrina', 1954, 1,'NR', 113, 'Classic');
INSERT INTO film VALUES ('15W', 'Wide Screen', 'Breakfast at Tiffany', 1961, 1, 'NR', 115, 'Classic');
INSERT INTO film VALUES ('16W', 'Wide Screen', 'My Fair Lady', 1964, 1, 'G', 172, NULL);
INSERT INTO film VALUES ('17F', 'Full Screen', 'The Heart is a Lonely Hunter', 1968, 1, null, 123, 'Drama');
INSERT INTO film VALUES ('23W', 'Full Screen', 'Titanic: The Complete Story', 1994, 2,'NR', 300, 'Documentary');
INSERT INTO film VALUES ('24F', 'Full Screen', 'Rush Hour', 1998, 1, 'PG-13', 98, 'Comedy');
INSERT INTO film VALUES ('28W', 'Wide Screen', 'Pearl Harbor', 2001, 1, 'PG-13', 183, 'War');
INSERT INTO film VALUES ('31W', 'Wide Screen', 'Avatar', 2010, 3,'PG-13', 162,'Sci-Fi');
INSERT INTO film VALUES ('38W', 'Wide Screen', 'Star Wars: The Force Awakens', 2016, 3,'PG-13', 136,'Sci-Fi');
INSERT INTO film VALUES ('40W', 'Wide Screen', 'Harry Potter and the Deathly Hollows: Part I', 2011, 1, 'PG-13', 146, 'Fantasy');
INSERT INTO film VALUES ('41W', 'Multiple Formats', 'Transformers: Age of Extinction', 2014, 1,'PG-13', 164,'Action and Adventure');
INSERT INTO film VALUES ('42F', 'Wide Screen', 'Horrible Bosses', 2011, 1, 'R', 98, 'Comedy');
INSERT INTO film VALUES ('43W', 'Wide Screen', 'Rogue One: A Star Wars Story', 2017, 3,'PG-13', 133,'Sci-Fi');
INSERT INTO film VALUES ('44W', 'Wide Screen', 'The Prince of Persia: The Sands of Time', 2010, 1,'PG-13', 116, 'Action and Adventure');
INSERT INTO film VALUES ('45W', 'Wide Screen', 'Clash of the Titans', 2010, 1,'PG-13', 106, 'Action and Adventure');
INSERT INTO film VALUES ('46W', 'Wide Screen', 'Skyfall', 2012, 1, 'PG-13', 143, 'Action and Adventure');
INSERT INTO film VALUES ('47W', 'Wide Screen', 'Hugo', 2012, 1,'PG', 126,'Children and Family');
INSERT INTO film VALUES ('48W', 'Wide Screen', 'Brave', 2012, 1, 'PG', 93, 'Children and Family');
INSERT INTO film VALUES ('49W', 'Wide Screen', 'Zootopia', 2016, 1,'PG', 108,'Children and Family');
INSERT INTO film VALUES ('50W', 'Wide Screen', 'Star Trek', 2010, 1, 'PG-13', 127, 'Sci-Fi');
INSERT INTO film VALUES ('60W', 'Wide Screen', 'Harry Potter and the Deathly Hollows: Part II', 2012, 1, 'PG-13', 130, 'Fantasy');
INSERT INTO film VALUES ('61W', 'Multiple Formats', 'Guardians of the Galaxy', 2014, 1, 'PG-13', 121, 'Sci-Fi');
INSERT INTO film VALUES ('62W', 'Wide Screen', 'Alphas: Season 1', 2012, 3,'NR', 497,'TV Sci-Fi');
INSERT INTO film VALUES ('63W', 'Wide Screen', 'The Dark Knight Rises', 2012, 1, 'PG-13', 165, 'Action and Adventure');
INSERT INTO film VALUES ('64W', 'Wide Screen', 'The Avengers', 2012, 1, 'PG-13', 143, 'Action and Adventure');
INSERT INTO film VALUES ('65W', 'Wide Screen', 'Wrath of the Titans', 2012, 1, 'PG-13', 99, 'Action and Adventure');
INSERT INTO film VALUES ('66W', 'Multiple Formats', 'Scorpion: Season 1', 2015, 6,'NR', 916,'TV Drama');
INSERT INTO film VALUES ('67W', 'Wide Screen', 'Spectre', 2016, 1, 'PG-13', 150, 'Action and Adventure');
INSERT INTO film VALUES ('68W', 'Wide Screen', 'Alphas: Season 2', 2013, 3,'NR', 562,'TV Sci-Fi');
INSERT INTO film VALUES ('71W', 'Wide Screen', 'The Croods', 2013, 1, 'PG', 96, 'Children and Family');
INSERT INTO film VALUES ('72W', 'Wide Screen', 'Moana', 2017, 1,'PG', 107,'Children and Family');
INSERT INTO film VALUES ('73W', 'Wide Screen', 'A Good Day to Die Hard', 2013, 1, 'R', 97, 'Thriller');
INSERT INTO film VALUES ('74W', 'Wide Screen', 'Star Trek: Into Darkness', 2013, 1, 'PG-13', 132, 'Sci-Fi');
INSERT INTO film VALUES ('80W','Wide Screen', 'The Hunger Game: Catching Fire', 2014, 1,'PG-13', 146,'Sci-Fi');
INSERT INTO film VALUES ('81W','Wide Screen', 'The Hobbit: The Desolation of Smaug', 2014, 2,'PG-13', 161,'Fantasy');
INSERT INTO film VALUES ('82W','Wide Screen', 'The Hobbit: The Battle of the Five Armies', 2015, 2,'PG-13', 144,'Fantasy');
INSERT INTO film VALUES ('83W','Wide Screen', 'Lucy', 2015, 2,'R', 90,'Action and Adventure');
INSERT INTO film VALUES ('84M','Multiple Formats', 'Star Trek Beyond',2016,2,'PG-13',122,'Sci-Fi');
答案 0 :(得分：1)
您可以使用sign()（在数学中代表signum）函数来导出所需的列：
sum(decode (sign(year - 2015), -1 , 1, 0)) as Before2015
您可以使用此查询
select decode(substr(genre,1,7),'Classic','Classic',genre),
sum(decode (sign(year - 2015), -1 , 1, 0)) as Before2015,
sum(decode (year, 2015, 1, 0)) Year2015,
sum(decode (year, 2016, 1, 0)) Year2016,
sum(decode (year, 2017, 1, 0)) Year2017
from film
group by rollup(decode(substr(genre,1,7),'Classic','Classic',genre))
组合所有Classic类型的电影。