SQL能夠做出正確的計數

Question

有SQLite表：

orderitems 
-id 
-item_id 
-quantity 

我要統計每個ITEM_ID 這並不是一個問題：

$this->db->query("SELECT item_id,COUNT(item_id) 
        FROM sh_orderitems 
        GROUP by item_id 
        ORDER by COUNT(item_id) DESC LIMIT 5")->fetchAll(); 

結果是：

0 => 
array (size=4) 
    'item_id' => string '38' (length=2) 
    0 => string '38' (length=2) 
    'COUNT(item_id)' => string '3' (length=1) 
    1 => string '3' (length=1) 

但這不是一個好的解決方案，原因是：數量計算。 需要這樣的東西SELECT ITEM_ID，COUNT（ITEM_ID）*數量

Answer 1

如果YOUT計數行和秩序由數..

SELECT item_id,SUM(quantity) as `sum_items` 
        FROM sh_orderitems 
        GROUP by item_id 
        ORDER by `sum_items` DESC LIMIT 5 

或

SELECT item_id,sum_items 
     FROM (SELECT item_id, SUM(quantity) AS sum_items 
        FROM sh_orderitems 
        GROUP by item_id) 
     ORDER by sum_items DESC LIMIT 5