Question

我有两个表类别和产品。类别表有id，name和product表有id，cat_id，name，details等。我需要一个mysql查询，它将选择属于每个类别的每个类别和产品总数，并按总计数排序结果。任何人都可以帮助我吗？

类别表

+----+------+
| id | name |
+----+------+
|  1 | cat1 |
|  2 | cat2 |
|  3 | cat3 |
+----+------+

产品表

+----+-------+--------+   
| id | name  | cat_id |    
+----+-------+--------+
|  1 | prod1 |      1 |    
|  2 | prod2 |      1 |    
|  3 | prod3 |      3 |    
|  4 | prod4 |      2 |    
|  5 | prod5 |      2 |
|  6 | prod6 |      2 |    
+----+-------+--------+

预期输出表

+----+------+-------+    
| id | name | count |    
+----+------+-------+    
|  2 | cat2 |     3 |    
|  1 | cat1 |     2 |    
|  3 | cat3 |     1 |  
+----+------+-------+

Answer 1

我不知道小组是否有错误。但试试吧

    select b.cnt,a.name from Category as a left join 
    (select count(*) as cnt,c.name,c.id  from Product as p 
    left join Category as c.id = p.cat_id group by p.cat_id) 
     as b b.id = a.id order by cnt

Answer 2

解决方案：

SELECT c.id category_id, c.name category_name, count( p.cat_id ) product_count
FROM categories c
INNER JOIN products p ON c.id = p.cat_id
GROUP BY p.cat_id
ORDER BY product_count DESC

和结果：

+-------------+---------------+---------------+
| category_id | category_name | product_count |
+-------------+---------------+---------------+
|           1 | cat1          |             7 |
|           2 | cat2          |             6 |
|           3 | cat3          |             3 |
+-------------+---------------+---------------+

没有LEFT JOIN

Mysql查询选择类别表中的所有项目以及属于按总计数排序的每个类别的产品表中的总项目

2 个答案: