-- 创建测试表 学习成绩统计表
CREATE TABLE ScoreStatistics
(
UserName NVARCHAR(20), --学生姓名
SubjectName NVARCHAR(30), --科目名称
Score FLOAT, --成绩
)
-- 插入测试数据
INSERT INTO ScoreStatistics SELECT '小王', '语文', 100
INSERT INTO ScoreStatistics SELECT '小王', '数学', 90.5
INSERT INTO ScoreStatistics SELECT '小王', '英语', 88
INSERT INTO ScoreStatistics SELECT '小王', '历史', 65
INSERT INTO ScoreStatistics SELECT '小李', '语文', 81
INSERT INTO ScoreStatistics SELECT '小李', '数学', 99
INSERT INTO ScoreStatistics SELECT '小李', '英语', 95
INSERT INTO ScoreStatistics SELECT '小李', '历史', 90
INSERT INTO ScoreStatistics SELECT '小刘', '语文', 90
INSERT INTO ScoreStatistics SELECT '小刘', '数学', 85
INSERT INTO ScoreStatistics SELECT '小刘', '英语', 59
INSERT INTO ScoreStatistics SELECT '小刘', '历史', 98
-- 传统写法
select UserName,
max(case SubjectName when '语文' then Score else 0 end)语文,
max(case SubjectName when '数学'then Score else 0 end)数学,
max(case SubjectName when '英语'then Score else 0 end)英语,
max(case SubjectName when '历史'then Score else 0 end)历史
from ScoreStatistics
group by UserName
-- PIVOT 写法更简洁
SELECT * FROM ScoreStatistics
AS P
PIVOT
(
SUM(Score/*行转列后 列的值*/) FOR
p.SubjectName/*需要行转列的列*/ IN ([语文],[数学],[英语],历史
/*列的值*/)
) AS T
-- order by 语文 desc 具体科目排序
-- order by username desc -- 姓名排序
-- 动态拼接列的示例
DECLARE @sql_str VARCHAR(8000); -- 要执行的sql
--拿到数值列 [历史],[数学],[英语],[语文]
DECLARE @sql_col VARCHAR(8000);
SELECT @sql_col = ISNULL(@sql_col + ',','')
+ QUOTENAME(SubjectName)
FROM ScoreStatistics GROUP BY SubjectName;
print(@sql_col); -- 打印数值列,不必需
SET @sql_str = '
SELECT * FROM (
SELECT [UserName],[SubjectName],[Score] FROM [ScoreStatistics])
p PIVOT
(SUM([Score]) FOR [SubjectName] IN ( '+ @sql_col +') ) AS pvt
ORDER BY pvt.[UserName]'
PRINT (@sql_str);--打印执行的sql
EXEC (@sql_str);-- 执行查询
-- 插入测试表
CREATE TABLE ScoreSummary
(
UserName NVARCHAR(20), --学生姓名
数学 FLOAT, --数学成绩
英语 FLOAT, --英语成绩
语文 FLOAT, --语文成绩
历史 FLOAT, --历史成绩
)
-- 插入测试数据
INSERT INTO ScoreSummary SELECT '小李',81,99,95,90;
INSERT INTO ScoreSummary SELECT '小刘',90,85,59,98;
INSERT INTO ScoreSummary SELECT '小王',100,90.5,88,65;
-- 查询用法
select aa.UserName,aa.Score
from (select UserName,数学,英语,语文,历史 from dbo.ScoreSummary) as a
unpivot(
Score for ScoreSummary in
(数学,英语,语文,历史)
) as aa order by aa.UserName
输出结果:
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