如何返回sum（）的行

Question

我现在发现我的原始表结构不好，所以想改变它。 但是我很难设计查询来获得具有新结构的行的总数。

current structure: 
+----------+-------+-------+-------+-------+ 
| state | shop | item0 | item1 | item2 | 
+----------+-------+-------+-------+-------+ 
| 5  | 0 | 1 | 2 | 3 | 
| 5  | 1 | 1 | 2 | 3 | 
| 5  | 2 | 1 | 2 | 3 | 
| 4  | 3 | 1 | 2 | 3 | 
+----------+-------+-------+-------+-------+ 
(quantities of items at shop) 

我想改变这2个表：

shops table 
+---------+--------+ 
| shop_id | state | 
+---------+--------+ 
| 0 | 5 | 
| 1 | 5 | 
| 2 | 5 | 
| 3 | 4 | 
+---------+--------+ 

items table 
+------------+--------------+ 
| shop | item | quantity | 
+------------+--------------+ 
| 0 | 0 | 1  | 
| 0 | 1 | 2  | 
| 0 | 2 | 3  | 
| 1 | 0 | 1  | 
| 1 | 1 | 2  | 
| 1 | 2 | 3  | 
| 2 | 0 | 1  | 
| 2 | 1 | 2  | 
| 2 | 2 | 3  | 
| 3 | 0 | 1  | 
| 3 | 1 | 2  | 
| 3 | 2 | 3  | 
+------------+--------------+ 

旧的布局允许简单的查询，通过连续获得总计：

SELECT state,SUM(item0) t0,SUM(item1) t1,SUM(item2) t2 
FROM shops 
WHERE state=5 

    +--------+---------+---------+----------+ 
    | state | t0 | t1 | t2 | 
    +--------+---------+---------+----------+ 
    | 5 | 3 |  6 | 9  | 
    +--------+---------+---------+----------+ 

With the new structure, 
I can get the totals in column as follows: 

SELECT item,SUM(quantity) total 
FROM shops 
LEFT JOIN items ON shop=shopid 
WHERE state=5 
GROUP by item 
+--------+---------+ 
| item | total | 
+--------+---------+ 
| 0 | 3 | 
+--------+---------+ 
| 1 | 6 | 
+--------+---------+ 
| 2 | 9 | 
+--------+---------+ 

but how do I get the totals in rows: 
+--------+---------+---------+----------+ 
| state | t0 | t1 |  t2 | 
+--------+---------+---------+----------+ 
| 4 |  1 |  2 |  3 | 
| 5 |  3 |  6 |  9 | 
+--------+---------+---------+----------+ 

Answer 1

您可以尝试使用一些更JOIN s：

SELECT S.state, 
    SUM(T0.quantity) AS "T0", 
    SUM(T1.quantity) AS "T1", 
    SUM(T2.quantity) AS "T2" 
FROM shops AS S 
LEFT JOIN items AS T0 ON S.shop_id = T0.shop_id AND T0.item=0 
LEFT JOIN items AS T1 ON S.shop_id = T1.shop_id AND T1.item=1 
LEFT JOIN items AS T2 ON S.shop_id = T2.shop_id AND T2.item=2 
GROUP BY S.state 

可能有一个更简单的方法。