mysql - 如何查询可能不存在的多对多？

Question

假设我有这些表格和值

table actors
id  int  11  primary key auto_increment
name  varchar  30

table movies
id  int  11  primary key auto_increment
name  varchar  30

table actors_movies
actor_id  int  11
movie_id  int  11

我如何查询数据库以获取他们所在的所有 Actor 和电影？

例如，像这样:

从......(查询)......中选择actors.name，movies.name

输出会是这样的

actors.name movies.name movies.name movies.name
Bob         Movie A     NULL        NULL
Melissa     Movie A     Movie B     NULL
Rick        NULL        NULL        Movie C

Answer 1

逗号分隔:

SELECT actors.name, GROUP_CONCAT(movies.name)
FROM actors_movies
LEFT JOIN actors ON actors.id = actors_movies.actor_id
LEFT JOIN movies ON movies.id = actors_movies.movie_id
GROUP BY actors_movies.actor_id

输出将是这样的:

+-------------+---------------------------+
| name        | GROUP_CONCAT(movies.name) |
+-------------+---------------------------+
| Bob         | Movie A                   |
| Melissa     | Movie A,Movie B           |
| Rick        | Movie C                   |
+-------------+---------------------------+

SQLFiddle:http://sqlfiddle.com/#!9/04c0a2/1