Question

不确定为什么这不起作用......好像＆gt; = b是一个布尔表达式。 RDMS抱怨“＆gt; = 3”说“缺少关键字”。我遵循了语法here

这有效：

WHEN count(movie_num) 3 THEN 'Most Popular'

这不是：

WHEN count(movie_num) >=3 THEN 'Most Popular'

可能遗漏了一些明显的东西，所以我很抱歉，如果是这样的话。

完整查询

select movie_genre as "Movie Genre", 
count(movie_num) as "Number of Movies",
CASE count(movie_num)
    WHEN count(movie_num) >=3 THEN 'Most Popular'
    WHEN count(movie_num) >= 2 THEN 'Popular'
    ELSE 'Normal' END AS "Popularity Rating"
from movie 
group by movie_genre
order by count(movie_num) desc;

Answer 1

试试这个，

更改 CASE（movie_num）当计数（movie_num） 到 CASE WHEN count（movie_num）

select movie_genre as "Movie Genre", 
count(movie_num) as "Number of Movies",
     CASE WHEN count(movie_num) >=3 THEN 'Most Popular'
          WHEN count(movie_num) >= 2 THEN 'Popular'
     ELSE 'Normal' END AS "Popularity Rating"
from movie 
group by movie_genre
order by count(movie_num) desc;

Answer 2

根据您的条件，您可以重写它以使用simple-case expression：

select movie_genre as "Movie Genre", 
       count(movie_num) as "Number of Movies",
       CASE count(movie_num)
         WHEN 0 THEN 'Normal'
         WHEN 1 THEN 'Normal'
         WHEN 2 THEN 'Popular'
         ELSE 'Most Popular'
       END AS "Popularity Rating"
from movie 
group by movie_genre
order by count(movie_num) desc;

Oracle CASE和BOOLEAN数字表达式

2 个答案: