2015-09-23 24 views
0

問題:我想知道什麼是被分配給每個類別根據他們的記錄中最流行的類別選擇基於分配給他們的記錄最流行的類別

數據庫結構:

categories.id 
categories.title 

records.id 
records.category_id 
records.title 
records.views 

目標:比方說,有1000多個項目中records表,這是不同的分配給EAC h類,並有隨機數records.views。我知道如何加入多個表格,但我不知道如何計算每個類別中記錄的所有視圖並顯示。

預期結果:我希望有輸出這樣的事情,如下圖所示:

CATEGORY #1 
    id = 21 
    title = Fruits 
    views = 381 

CATEGORY #2 
    id = 24 
    title = Snacks 
    views = 8875 

CATEGORY #3 
    id = 47 
    title = Toys 
    views = 381 

CATEGORY #4 
    id = 25 
    title = Milky-wilky products 
    views = 8875 

任何提示,如何實現這一目標?

回答

4

這似乎是與聚集一個非常簡單的查詢:

SELECT 
    c.id, c.title, SUM(r.views) AS views 
FROM 
    categories AS c 
    LEFT JOIN 
    records AS r 
     ON r.category_id = c.id 
GROUP BY 
    c.id, c.title ;