如何按计数和类别获取数据

Question

如果我有一张如下表格

Person   |   Category    | Fav Colors
-----    | -----------   | ------
 one     |   Native      |  RED
 one     |   Native      |  GREEN
 two     |   Non-Native  |  RED
 two     |   Non-Native  |  BLUE
 three   |   Native      |  RED
 three   |   Native      |  GREEN

如何根据每种颜色的每个类别的人数来获取数据？

即。

Fav Color | Native  | Non-Native
--------- | --------| --------
RED       | 2       | 1
GREEN     | 2       | 0
BLUE      | 0       | 1

Answer 1

你可以这样做：

select   `Fav Colors` as `Fav Color`,
         count(case category when 'Native' then 1 end) Native,
         count(case category when 'Non-Native' then 1 end) `Non-Native`
from     tbl
group by `Fav Colors`

SQL Fiddle

注意：您没有提及排序顺序的任何要求。如果您需要一个，您只需列出order by子句中的列号：

order by 2 desc

Answer 2

我是在Oracle中完成的，所以不得不稍微重命名列，但这里有一个想法：

select FAV_COLORS,SUM(CASE CATEGORY WHEN 'NATIVE' THEN 1 ELSE 0 END) AS NATIVE,SUM(CASE CATEGORY WHEN 'NON-NATIVE' THEN 1 ELSE 0 END) AS NON_NATIVE
from TEMP
GROUP BY FAV_COLORS