加入并显示两个表中的信息

Question

我有两张桌子：

1. category

   +----+------+
   | ID | Name |
   +----+------+
   |  1 | news |
   |  2 | blog |
   +----+------+
   

2. articles

   +----+----------+---------------+
   | ID | category |     title     |
   +----+----------+---------------+
   |  1 |        1 | hello         |
   |  2 |        2 | yamen         |
   |  3 |        2 | stackoverflow |
   |  4 |        1 | nice day      |
   +----+----------+---------------+
   

现在我需要显示每个类别名称及其中的文章总数。

Answer 1

您只需要加入表格并使用适当的聚合函数对结果进行分组：

SELECT   category.name, COUNT(articles.ID)
FROM     category LEFT JOIN articles ON articles.category = category.ID
GROUP BY category.ID

Answer 2

 Select c.ID,  
 c.category, 
 count(a.title) as titlecount, 
 GROUP_CONCAT(a.title SEPARATOR ',') as titles
 FROM category c
 INNER JOIN article a on c.ID = a.category
 group by c.ID