计算类型项的总和

Question

我该怎么做才是这样：

|type|quantity|
+----+--------+
|shoe| 10     |
|hat | 2      |
|shoe| 7      |
|shoe| 1      |
|hat | 5      |

得到这个：

|shoes|hats|
+-----+----+
| 18  | 7  |

我该怎么做？到目前为止，我还没有提出一个有效的查询，我认为应该看起来像这样：

 SELECT 
   SUM(CASE type WHEN 'shoe' then quantity ELSE 0 END) AS "shoes",
   SUM(CASE type WHEN 'hat' then quantity ELSE 0 END) AS "hats"
 FROM items 
 GROUP BY type

Answer 1

只需删除group by即可。您只想要一行：

 SELECT 
   SUM(CASE type WHEN 'shoe' then quantity ELSE 0 END) AS "shoes",
   SUM(CASE type WHEN 'hat' then quantity ELSE 0 END) AS "hats"
 FROM items ;