使用 PIVOT 的 SQL 查询

Posted 2023-02-15

【中文标题】使用 PIVOT 的 SQL 查询

【英文标题】：SQL query with PIVOT

【发布时间】：2021-12-25 08:05:36

【问题描述】：

数据：

CREATE TABLE [dbo].[Grade_Report](
    [Student] [varchar](50) NULL,
    [Subject] [varchar](50) NULL,
    [Grades] [numeric](18, 2) NULL,
    [Semester] [int] NULL
);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jamie', N'Mathematics', CAST(82.00 AS Numeric(18, 2)), 1);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jamie', N'Science', CAST(83.00 AS Numeric(18, 2)), 1);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jamie', N'Programming', CAST(91.00 AS Numeric(18, 2)), 1);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jamie', N'History', CAST(89.00 AS Numeric(18, 2)), 1);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jamie', N'English', CAST(95.00 AS Numeric(18, 2)), 1);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jamie', N'Mathematics', CAST(79.00 AS Numeric(18, 2)), 2);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jamie', N'Science', CAST(80.00 AS Numeric(18, 2)), 2);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jamie', N'Programming', CAST(92.00 AS Numeric(18, 2)), 2);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jamie', N'History', CAST(95.00 AS Numeric(18, 2)), 2);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jamie', N'English', CAST(93.00 AS Numeric(18, 2)), 2);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jenny', N'Mathematics', CAST(95.00 AS Numeric(18, 2)), 1);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jenny', N'Science', CAST(95.00 AS Numeric(18, 2)), 1);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jenny', N'Programming', CAST(90.00 AS Numeric(18, 2)), 1);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jenny', N'History', CAST(92.00 AS Numeric(18, 2)), 1);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jenny', N'English', CAST(96.00 AS Numeric(18, 2)), 1);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jenny', N'Mathematics', CAST(78.00 AS Numeric(18, 2)), 2);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jenny', N'Science', CAST(79.00 AS Numeric(18, 2)), 2);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jenny', N'Programming', CAST(82.00 AS Numeric(18, 2)), 2);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jenny', N'History', CAST(80.00 AS Numeric(18, 2)), 2);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jenny', N'English', CAST(79.00 AS Numeric(18, 2)), 2);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jerome', N'Mathematics', CAST(96.00 AS Numeric(18, 2)), 1);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jerome', N'Science', CAST(92.00 AS Numeric(18, 2)), 1);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jerome', N'Programming', CAST(93.00 AS Numeric(18, 2)), 1);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jerome', N'History', CAST(88.00 AS Numeric(18, 2)), 1);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jerome', N'English', CAST(94.00 AS Numeric(18, 2)), 1);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jerome', N'Mathematics', CAST(90.00 AS Numeric(18, 2)), 2);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jerome', N'Science', CAST(92.00 AS Numeric(18, 2)), 2);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jerome', N'Programming', CAST(98.00 AS Numeric(18, 2)), 2);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jerome', N'History', CAST(93.00 AS Numeric(18, 2)), 2);
INSERT [dbo].[Grade_Report] ([Student], [Subject], [Grades], [Semester]) VALUES (N'Jerome', N'English', CAST(90.00 AS Numeric(18, 2)), 2);


SELECT * FROM Grade_Report;

查询：

SELECT Student, [English], [Mathematics], [Science], [Programming], [History]
FROM
(
    SELECT Grades, Subject FROM Grade_Report
)AS SourceTable
PIVOT
(
    AVG(Grades)
    FOR Subject IN([English], [Mathematics], [Science], [Programming], [History])
)AS PivotTable;

Student 突出显示为无效的列名，当我从查询中删除 Student 并执行时，输出如下：

我尝试在查询中以任何方式输入和输出学生列，但它给出了错误。我想要的输出是将科目显示为列，并显示两个学期学生的计算平均成绩。像这样：

【问题讨论】：

您是否尝试在SourceTable 查询的选定列中包含Student？在pivot 操作中，枢轴列需要围绕某些东西进行旋转，在这种情况下，就是您的Student 值。

【参考方案1】：

将学生的姓名放在子查询中 从 ( 从 Grade_Report 中选择 学生、 成绩、科目 )AS SourceTable

SELECT Student, [English], [Mathematics], [Science], [Programming], 
[History]
FROM
(
    SELECT Student, Grades, Subject FROM Grade_Report
)AS SourceTable
PIVOT
(
    AVG(Grades)
    FOR Subject IN([English], [Mathematics], [Science], [Programming], 
    [History])
)AS PivotTable;