mysql - 在一行中从一对多关系中获取所有值

Question

我的数据库中有一对多的关系。

我想获取所有城市，所有的电影院都以 CSV 格式附加在一行中。我试过了：

SELECT city.*,CONCAT(cinema_name)
FROM city
LEFT JOIN cinema
ON cinema.city_id=city.city_id
GROUP BY city.city_id

但这只会返回第一个电影院。

Answer 1

使用 GROUP_CONCAT 而不是 CONCAT

SELECT
  city.*,
  GROUP_CONCAT(cinema_name) AS `Cinemas`
FROM city
  LEFT JOIN cinema
    ON cinema.city_id = city.city_id
GROUP BY city.city_id

Answer 2

试试这个查询

SELECT ct.city_id, GROUP_CONCAT(cinema_name) 
FROM cinema c, city ct
WHERE c.city_id = ct.city_id
Group BY c.city_id;

Answer 3

对于在V5.7上测试的当前版本的 Mysql，如果您希望将该数据作为 json 对象，您可以试试这个。

SELECT
  city.*,
  GROUP_CONCAT(
JSON_OBJECT(
'cinema_name', cinema_name
)) AS `Cinemas`
FROM city
  LEFT JOIN cinema
    ON cinema.city_id = city.city_id
GROUP BY city.city_id