选择COUNT个内联接

Question

我有两个表：

project (id, name)
list (id, name, project_id)

我想将每个项目和列表号都放入该项目。

我尝试过：

SELECT project.id, project.name, COUNT(list.id) AS list_count
FROM project 
INNER JOIN list ON (list.project_id = project.id)
GROUP BY project.id DESC

但是我只得到有清单的项目。

如果该项目没有列表，我不会得到...

如果COUNT（list_id）= 0，我希望list_count = 0，我该怎么办？

Answer 1

使用左联接代替内联接

SELECT project.id, project.name, COUNT(list.id) AS list_count
FROM project 
Left JOIN list ON (list.project_id = project.id)
GROUP BY project.id DESC