一个 SQL 查询的多个输出

Question

我正在尝试编写一个 SQL 查询，该查询将根据数据库中特定数量存在的次数输出多个变量。然后，此信息将用于图表。

数据库设置如下：

ID | quantity | etc..
---------------------
1  |   2      |
2  |   6      |
3  |   1      |
4  |   2      |
.
.
.

这是我的查询：

SELECT 
  COUNT(CASE WHEN quantity = 1) AS quantity1, 
  COUNT(CASE WHEN quantity = 2) AS quantity2
FROM orders

但我希望它像这样输出：

quantity1 | quantity2
---------------------
    1     |   2      |

相反，我收到以下错误消息：

提前致谢！

编辑：如果您想在我的数据库上测试您的代码，链接如下...

-链接已删除-

Answer 1

这是另一种方法，也许有帮助：

SELECT SUM(CASE WHEN quantity = 1 THEN 1 ELSE 0 END) AS quantity_1,
       SUM(CASE WHEN quantity = 2 THEN 1 ELSE 0 END) AS quantity_2,
       SUM(CASE WHEN quantity = 3 THEN 1 ELSE 0 END) AS quantity_3,
       SUM(CASE WHEN quantity = 4 THEN 1 ELSE 0 END) AS quantity_4,
       SUM(CASE WHEN quantity = 5 THEN 1 ELSE 0 END) AS quantity_5,
       SUM(CASE WHEN quantity = 6 THEN 1 ELSE 0 END) AS quantity_6,
       SUM(CASE WHEN quantity > 6 THEN 1 ELSE 0 END) AS quantity_more_than_6
  FROM orders

这是一个针对 MS Access 的特殊查询：

SELECT SUM(SWITCH(quantity = 1, 1)) AS quantity_1,
       SUM(SWITCH(quantity = 2, 1)) AS quantity_2,
       SUM(SWITCH(quantity = 3, 1)) AS quantity_3,
       SUM(SWITCH(quantity = 4, 1)) AS quantity_4,
       SUM(SWITCH(quantity = 5, 1)) AS quantity_5,
       SUM(SWITCH(quantity = 6, 1)) AS quantity_6,
       SUM(SWITCH(quantity > 6, 1)) AS quantity_more_than_6
  FROM orders

Answer 2

使用 GROUP BY 子句，例如：

SELECT quantity, COUNT(*) AS num
FROM Orders
GROUP BY quantity
HAVING COUNT(*) > 6;

编辑：您可以添加 HAVING 子句