Question

分类表：

id, name
---------
1   cat1
2   cat2
3   cat3 
4   cat4

文章表：

id, cid, title
--------------
1   1    title1
2   3    title2
3   1    title3
4   2    title4

如何选择MySQL中每个类别文章的所有类别和计数？我需要一个mysql查询，它将选择属于每个类别的文章的所有类别和总数，并按类别ID排序。

预期输出表：

+-------+-------+    
|  name | count |    
+-------+-------+    
|  cat1 |     2 |    
|  cat2 |     1 |    
|  cat3 |     1 |  
|  cat4 |     0 |  
+-------+-------+

Answer 1

SELECT
    c.`name`,
    COUNT(a.cid) AS `count`
FROM
    categories c
    LEFT JOIN article a ON c.id = a.cid
GROUP BY
    c.`name`
ORDER BY
    c.`name`

Answer 2

试试这个：

SELECT c.`name`, count(a.cid) as count FROM category
LEFT JOIN article
ON c.id = a.cid
GROUP BY a.cid

Answer 3

select c.name,count(b.title)count from category a, article b where c.id = a.cid group by c.name order by a.cid;

Answer 4

我希望这会奏效。请检查。

select Category.name. ifnull(count(Article.cid),0) as count FROM Category LEFT JOIN Article on Article.cid=Category.id group by Category.Id

Answer 5

您也可以使用

之类的子查询

arr[1,:].sort()

如何选择MySQL中每个类别文章的所有类别和计数

5 个答案: