用3個表格計算項目

Question

我嘗試計算3個表格中項目的數量和百分比。

表：

categories 
cat_id | title 
1  | phone 
2  | tablet 

products 
prod_id | cat_id | title 
1001  | 1  | iphone 
1002  | 1  | nokia 
1003  | 1  | blackberry 
1004  | 2  | ipad 

user_products 
id  | prod_id | user_id 
1  | 1001  | 1 
2  | 1001  | 2 
3  | 1001  | 3 
4  | 1003  | 3 
5  | 1004  | 4 

我到目前爲止有：

SELECT categories.cat_id, products.title, COUNT(products.title) AS cnt 
FROM categories 
LEFT JOIN products ON categories.cat_id = products.cat_id 
GROUP BY products.title 

期望的結果：

Tablets: 
Ipad  | 1 | 100% 

Phones: 
Iphone  | 3 | 75% 
Blackberry | 1 | 25% 

Answer 1

SELECT c.cat_id, c.title AS cat_name, p.prod_id, p.title AS prod_name, 
     COUNT(*) AS cnt, 
     100*COUNT(*)/cat_total AS pct 
FROM products AS p 
INNER JOIN user_products AS up ON p.prod_id = up.prod_id 
INNER JOIN (SELECT c.cat_id, c.title, COUNT(*) AS cat_total 
      FROM categories AS c 
      JOIN products AS p ON c.cat_id = p.cat_id 
      JOIN user_products AS up ON up.prod_id = p.prod_id 
      GROUP BY c.cat_id) AS c ON c.cat_id = p.cat_id 
GROUP BY p.prod_id 
ORDER BY cat_name, cnt DESC 

DEMO

Answer 2

試試這個

SELECT 
    categories.cat_id, 
    products.title, 
    COUNT(user_products.id) AS cnt, 
    ROUND(((
      COUNT(user_products.prod_id)/ 
      (
       SELECT COUNT(user_products.id) 
        FROM user_products 
      INNER JOIN products ON products.prod_id = user_products.prod_id 
       WHERE products.cat_id = categories.cat_id 
       GROUP BY products.cat_id 
      )) * 100), 2) as percent 
FROM user_products 
INNER JOIN products ON products.prod_id = user_products.prod_id 
INNER JOIN categories ON categories.cat_id = products.cat_id 
GROUP BY products.prod_id, categories.cat_id 

Answer 3

在這裏你去！

SELECT c.title AS category, p.title AS device, 
COUNT(up.prod_id) AS totalDevices,(COUNT(up.prod_id)/totNumDev)*100 AS percent 
FROM user_products AS up , products AS p , categories AS c, 

(SELECT _p.cat_id AS q2Cat, COUNT(_up.prod_id) AS totNumDev 
FROM user_products AS _up, products AS _p WHERE _p.prod_id = _up.prod_id 
GROUP BY _p.cat_id) AS query2 

WHERE p.prod_id = up.prod_id AND c.cat_id = p.cat_id AND query2.q2Cat = c.cat_id 
GROUP BY up.prod_id;