MySQL return 输出为空集

Question

我有 movie 作为我的 table

我尝试执行以下查询，其中包含 movie_genre='comedy' 和 movie_genre='family' 的 2 个条件：

select movie_title, movie_cost, movie_genre
from movie
where movie_genre ='comedy'
and movie_genre ='family'
order by movie_cost asc;

执行查询后 return Empty set。虽然我尝试了一个条件它正常工作但是当添加 2 个条件时它再次出错。

我该如何解决这个问题？

Answer 1

SELECT movie_title, movie_cost, movie_genre
FROM movie
WHERE
   movie_genre ='comedy'
OR 
   movie_genre ='family'
ORDER BY movie_cost ASC;

你应该使用OR因为AND意味着两个条件必须同时为真，但那是不可能的！

不同的查询语法可以是

SELECT movie_title, movie_cost, movie_genre
FROM movie
WHERE movie_genre IN ('comedy', 'family')
ORDER BY movie_cost ASC;

Answer 2

您必须使用 OR 来检查 movie_genre 是否是两个值中的一个。

更新查询 -

select movie_title, movie_cost, movie_genre from movie
where movie_genre ='comedy' or movie_genre ='family'
order by movie_cost asc;

Answer 3

还有一个选项是 UNION ALL:

SELECT movie_title, movie_cost, movie_genre
FROM movie
WHERE movie_genre = 'comedy'
UNION ALL
SELECT movie_title, movie_cost, movie_genre
FROM movie
WHERE movie_genre = 'family'
ORDER BY movie_cost ASC;

MySQL return 输出为空集

MySQL return output in empty set

mysql

is-empty