Question

源表：

Student_ID主题_ID主题标记
1 ------------ 10 ------------ Chem-82
1 ------------ 11 ------------ Phy ---- 89
1 ------------ 12 ------------数学-88
1 ------------ 13 ------------工程---- 80

目标表如下：

Student_ID Phy Chem Maths Eng
1 ------------- 82-- 89 --- 88 ---- 80

注意：这些“-”仅用于描述表格。抱歉，格式错误。

Answer 1

您可以使用case表达式进行有条件的聚合：

select student_id, 
       sum(case when Subject _ID = 10 then marks else 0 end) as Chem,
       sum(case when Subject _ID = 11 then marks else 0 end) as Phy,
       sum(case when Subject _ID = 12 then marks else 0 end) as Maths,
       sum(case when Subject _ID = 13 then marks else 0 end) as Eng
from table t
group by student_id;

Answer 2

您正在寻找创建动态枢纽的能力。

CREATE TABLE #T1 (StudentID int,SubjectID INT, Subject varchar(10), Marks int)
INSERT INTO #T1 VALUES (1, 10, 'Chem',82)
INSERT INTO #T1 VALUES (1,11, 'Phy',89)
INSERT INTO #T1 VALUES (1,12, 'Maths',88)
INSERT INTO #T1 VALUES (1,13, 'Eng',80)
INSERT INTO #T1 VALUES (2, 10, 'Chem',80)
INSERT INTO #T1 VALUES (2,11, 'Phy',85)
INSERT INTO #T1 VALUES (2,12, 'Maths',91)
INSERT INTO #T1 VALUES (2,13, 'Mgmt',82)
DECLARE @PivotColumnHeaders varchar(MAX)
SELECT @PivotColumnHeaders =
  COALESCE(
    @PivotColumnHeaders + ',[' + UC.Subject + ']',
    '[' + Subject + ']'
  )
FROM (SELECT Subject FROM #T1 GROUP BY Subject) UC

DECLARE @PQuery varchar(MAX) = '
SELECT * FROM (SELECT StudentID, Subject, Marks FROM #T1 T0) T1
PIVOT (SUM([Marks]) FOR Subject IN (' + @PivotColumnHeaders + ') ) AS P'
EXECUTE (@PQuery)

DROP TABLE #T1

结果是：

StudentID   Chem    Eng   Maths  Mgmt   Phy
   1         82      80     88   NULL    89
   2         80     NULL    91    82     85

将一个表的行转换为另一表的列。正文中提供了说明

2 个答案: