Question

我想从父行返回行，其中子行数与父ID相关。不幸的是，我遇到了一个问题，我的查询只返回带子行的行，没有子行的行不会返回结果。我尝试过LEFT，RIGHT，OUTER和INNER联接无济于事。 SQLFiddle链接和查询如下：

SELECT t.id, t.name, COUNT(s.id) AS cnt FROM top AS t 
JOIN sub AS s ON t.id = s.top_id GROUP BY t.id, t.name 
ORDER BY t.id ASC

http://sqlfiddle.com/#!9/c466fe/1

提前感谢您的帮助！

Answer 1

似乎你需要LEFT JOIN

http://sqlfiddle.com/#!9/c466fe/4

SELECT t.id, 
       t.name, 
       COUNT(s.id) AS cnt 
FROM top AS t 
LEFT JOIN sub AS s 
ON t.id = s.top_id 
GROUP BY t.id, t.name 
ORDER BY t.id ASC

Answer 2

SELECT t.id, t.name, COUNT(s.id) AS cnt 
FROM top AS t 
left JOIN sub AS s ON t.id = s.top_id GROUP BY t.id, t.name 
ORDER BY t.id ASC

查询已连接表的计数不显示零计数结果

2 个答案: