php - SQL 左连接只返回一行而不是多行

Question

我有两张表，一张有城市(id 和城市名称)，一张有城市图片(city_id 等)。

假设我正在寻找名为 Sibiu 的城市。这应该返回 3 个结果，因为表中还有更多类似的城市(Miercurea Sibiului、Sibiu、Poiana Sibiului)，但它只返回一个。

另外，请注意，timeline_elements 还没有城市的任何照片。

SELECT cities_countries.*, COUNT(timeline_elements.city_id) as number_of_photos 
FROM cities_countries   
LEFT JOIN timeline_elements on (cities_countries.id = timeline_elements.city_id)
WHERE cities_countries.name LIKE '%Sibiu%'

Answer 1

添加 GROUP BY 并显式提及 cities_countries 表的所有列名。我认为这些是 cities_countries 表中的列。 id、city_id、city_name。

同时为每个表设置别名以提高可读性。

SELECT C.id, C.city_id, C.city_name, ....
       , COUNT(T.city_id) as number_of_photos 
FROM cities_countries C  
LEFT JOIN timeline_elements T ON C.id = T.city_id
WHERE C.name LIKE '%Sibiu%'
GROUP BY C.id, C.city_id, C.city_name, ....