sql - 将元组值转换为列名

Question

有这样的东西:

+-------+------+-------+
| count |  id  | grade |
+-------+------+-------+
|     1 |    0 | A     |
|     2 |    0 | B     |
|     1 |    1 | F     |
|     3 |    1 | D     |
|     5 |    2 | B     |
|     1 |    2 | C     |

我需要:

+-----+---+----+---+---+---+
| id  | A | B  | C | D | F |
+-----+---+----+---+---+---+
|   0 | 1 |  2 | 0 | 0 | 0 |
|   1 | 0 |  0 | 0 | 1 | 1 |
|   2 | 0 |  5 | 1 | 0 | 0 |

我不知道我能不能做到这一点。我可以按 ID 分组，但您如何读取每个成绩列的计数值？

Answer 1

CREATE TABLE #MyTable(_count INT,id INT , grade VARCHAR(10))

INSERT INTO #MyTable( _count ,id  , grade )
SELECT 1,0,'A' UNION ALL
SELECT 2,0,'B' UNION ALL
SELECT 1,1,'F' UNION ALL
SELECT 3,1,'D' UNION ALL
SELECT 5,2,'B' UNION ALL
SELECT 1,2,'C' 


SELECT *
FROM
(
 SELECT _count ,id  ,grade
 FROM #MyTable
)A
PIVOT
(
  MAX(_count) FOR grade IN ([A],[B],[C],[D],[F])
)P