SQL：ステートメントは、最初の行だけの小計を返し

Question

私は以下のようなサンプルデータを持っている：

と私は以下のSQL文を使用します。

select a.product_category_id, b.Favorite, c.In_Cart,d.Pre_sales_order, 
     sum(b.Favorite)+sum(c.In_Cart)+sum(d.Pre_sales_order) as SubTotal 
from 
    (select distinct product_category_id 
    from item_activity 
    where last_item_status_code in (6,7,8) 
) a 
left join 
    (select product_category_id, count(last_item_status_code) as Favorite 
    from .item_activity 
    where last_item_status_code='6' 
    group by product_category_id 
) b on a.product_category_id=b.product_category_id 
left join 
    (select product_category_id, count(product_category_id) as In_Cart 
    from item_activity 
    where last_item_status_code='7' 
    group by product_category_id 
) c on c.product_category_id=a.product_category_id 
left join 
    (select product_category_id, count(product_category_id) as Pre_sales_order 
    from item_activity 
    where last_item_status_code='8' 
    group by product_category_id 
) d on d.product_category_id=a.product_category_id 
group by a.product_category_id 
; 

をし、この達成：

を

しかし、それは私に最初の行の小計を与えます....

Answer 1

はこれを試してみてください：

select product_category_id, 
    sum(case when last_item_status_code=6 then 1 else 0 end) As Favorite, 
    sum(case when last_item_status_code=7 then 1 else 0 end) As In_Cart, 
    sum(case when last_item_status_code=8 then 1 else 0 end) As Pre_sales_order, 
    count(last_item_status_code) as SubTotal 
from item_activity 
where last_item_status_code in (6,7,8) 
group by product_category_id; 

Answer 2

product_category_idは、他のテーブルに存在しません。したがって、小計はNULLになります。

SUM（1 + NULL）== NULL。 IFまたはCOALESCEを使用してNULLを0に変換することができます。