Question

我需要按UniqueIdentifier列进行分组，该表还包含XML列。

表架构： StudentMark ：

CREATE TABLE [dbo].[StudentMark]
(
    [StudentMarkId] [int] IDENTITY(1,1) NOT NULL,
    [StudentId] [uniqueidentifier] NULL,
    [SubjectId] [uniqueidentifier] NULL,
    [ScoreInfo] [xml] NULL,
    [GeneratedOn] [datetime2](2) NOT NULL,

    CONSTRAINT [PK_StudentMark] 
       PRIMARY KEY CLUSTERED ([StudentMarkId] ASC)
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]

示例种子数据

INSERT INTO [dbo].[StudentMark] ([StudentId], [SubjectId], [ScoreInfo], GeneratedOn])
VALUES ('FC3CB475-B480-4129-9190-6DE880E2D581', '0D72F79E-FB48-4D3E-9906-B78A9D105081', '<StudentMarkAttribute xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"></StudentMarkAttribute>', '2017-08-10 10:20:15'),
       ('0F4EF48C-93E3-41AA-8295-F6B0E8D8C3A2', '0D72F79E-FB48-4D3E-9906-B78A9D105081', '<StudentMarkAttribute xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"></StudentMarkAttribute>', '2017-08-10 10:20:15'),
       ('0F4EF48C-93E3-41AA-8295-F6B0E8D8C3A2', 'AB172272-D2E9-49E1-8040-6117BB6743DB', '<StudentMarkAttribute xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"></StudentMarkAttribute>', '2017-08-16 09:06:20'),
       ('FC3CB475-B480-4129-9190-6DE880E2D581', 'AB172272-D2E9-49E1-8040-6117BB6743DB', '<StudentMarkAttribute xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"></StudentMarkAttribute>', '2017-08-16 09:06:20');

要求：我需要按[dbo].[StudentMark].[StudentId]分组并获取最新记录。

我尝试了以下SQL查询，但它导致错误

SELECT 
    MAX([StudentMarkId]), [StudentId], [SubjectId], [ScoreInfo], [GeneratedOn]
FROM 
    [dbo].[StudentMark] 
GROUP BY 
    [StudentId]

错误：

列'dbo.StudentMark.SubjectId'在选择列表中无效，因为它不包含在聚合函数或GROUP BY子句中。

我审问了以下问题但我无法解决：Reason for Column is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause

请帮助我。

Answer 1

使用'Authorization': 'Basic ' + btoa(username + ':' + password)计算群组内的位置：

ROW_NUMBER

Answer 2

如果您有Students表格，则替代解决方案效果最佳：

select sm.*
from students s cross apply
     (select top 1 sm.*
      from studentmark sm
      where sm.studentid = s.studentid
      order by sm.generatedon desc
     ) sm;

Answer 3

您不能按XML或TEXT列进行分组，首先需要转换为varchar(max)：

SELECT 
    MAX([StudentMarkId]), [StudentId], [SubjectId],
    CONVERT(XML, CONVERT(VARCHAR(MAX), [ScoreInfo])) DetailXML,
    [GeneratedOn]
FROM 
    [dbo].[StudentMark] 
GROUP BY 
    [StudentId], [SubjectId], 
    CONVERT(VARCHAR(MAX), [ScoreInfo]), [GeneratedOn]

在第一行，它被转换为varchar（max）以匹配GROUP BY子句，稍后它将重新转换回XML。

如何按列分组 - SQL Server

3 个答案: