SQL 行列转换

模拟数据：

大多数数据库存储的数据都是这样，但是实际业务则需要我们对数据进行处理如下：

这就是很多时候面试也会遇到的列传行的问题。

创建数据库以及数据：

USE [master]
GO
/****** Object:  Database [MyStudy]    Script Date: 2018/6/5 23:27:15 ******/
CREATE DATABASE [MyStudy]
 CONTAINMENT = NONE
 ON  PRIMARY 
( NAME = N'MyStudy', FILENAME = N'E:DataMyStudy.mdf' , SIZE = 5120KB , MAXSIZE = UNLIMITED, FILEGROWTH = 1024KB )
 LOG ON 
( NAME = N'MyStudy_log', FILENAME = N'E:DataMyStudy_log.ldf' , SIZE = 2048KB , MAXSIZE = 2048GB , FILEGROWTH = 10%)
GO
ALTER DATABASE [MyStudy] SET COMPATIBILITY_LEVEL = 120
GO
IF (1 = FULLTEXTSERVICEPROPERTY('IsFullTextInstalled'))
begin
EXEC [MyStudy].[dbo].[sp_fulltext_database] @action = 'enable'
end
GO
ALTER DATABASE [MyStudy] SET ANSI_NULL_DEFAULT OFF 
GO
ALTER DATABASE [MyStudy] SET ANSI_NULLS OFF 
GO
ALTER DATABASE [MyStudy] SET ANSI_PADDING OFF 
GO
ALTER DATABASE [MyStudy] SET ANSI_WARNINGS OFF 
GO
ALTER DATABASE [MyStudy] SET ARITHABORT OFF 
GO
ALTER DATABASE [MyStudy] SET AUTO_CLOSE OFF 
GO
ALTER DATABASE [MyStudy] SET AUTO_SHRINK OFF 
GO
ALTER DATABASE [MyStudy] SET AUTO_UPDATE_STATISTICS ON 
GO
ALTER DATABASE [MyStudy] SET CURSOR_CLOSE_ON_COMMIT OFF 
GO
ALTER DATABASE [MyStudy] SET CURSOR_DEFAULT  GLOBAL 
GO
ALTER DATABASE [MyStudy] SET CONCAT_NULL_YIELDS_NULL OFF 
GO
ALTER DATABASE [MyStudy] SET NUMERIC_ROUNDABORT OFF 
GO
ALTER DATABASE [MyStudy] SET QUOTED_IDENTIFIER OFF 
GO
ALTER DATABASE [MyStudy] SET RECURSIVE_TRIGGERS OFF 
GO
ALTER DATABASE [MyStudy] SET  DISABLE_BROKER 
GO
ALTER DATABASE [MyStudy] SET AUTO_UPDATE_STATISTICS_ASYNC OFF 
GO
ALTER DATABASE [MyStudy] SET DATE_CORRELATION_OPTIMIZATION OFF 
GO
ALTER DATABASE [MyStudy] SET TRUSTWORTHY OFF 
GO
ALTER DATABASE [MyStudy] SET ALLOW_SNAPSHOT_ISOLATION OFF 
GO
ALTER DATABASE [MyStudy] SET PARAMETERIZATION SIMPLE 
GO
ALTER DATABASE [MyStudy] SET READ_COMMITTED_SNAPSHOT OFF 
GO
ALTER DATABASE [MyStudy] SET HONOR_BROKER_PRIORITY OFF 
GO
ALTER DATABASE [MyStudy] SET RECOVERY FULL 
GO
ALTER DATABASE [MyStudy] SET  MULTI_USER 
GO
ALTER DATABASE [MyStudy] SET PAGE_VERIFY CHECKSUM  
GO
ALTER DATABASE [MyStudy] SET DB_CHAINING OFF 
GO
ALTER DATABASE [MyStudy] SET FILESTREAM( NON_TRANSACTED_ACCESS = OFF ) 
GO
ALTER DATABASE [MyStudy] SET TARGET_RECOVERY_TIME = 0 SECONDS 
GO
ALTER DATABASE [MyStudy] SET DELAYED_DURABILITY = DISABLED 
GO
EXEC sys.sp_db_vardecimal_storage_format N'MyStudy', N'ON'
GO
USE [MyStudy]
GO
/****** Object:  Table [dbo].[Course]    Script Date: 2018/6/5 23:27:16 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Course](
    [ID] [int] IDENTITY(1,1) NOT NULL,
    [CourseName] [nvarchar](50) NULL,
 CONSTRAINT [PK_Course] PRIMARY KEY CLUSTERED 
(
    [ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO
/****** Object:  Table [dbo].[ScoreAndCourse]    Script Date: 2018/6/5 23:27:16 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[ScoreAndCourse](
    [CourseID] [int] NOT NULL,
    [StudentID] [int] NOT NULL,
    [ID] [int] IDENTITY(1,1) NOT NULL,
    [Number] [int] NOT NULL,
 CONSTRAINT [PK_Score] PRIMARY KEY CLUSTERED 
(
    [ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO
/****** Object:  Table [dbo].[Students]    Script Date: 2018/6/5 23:27:16 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Students](
    [Name] [nvarchar](50) NULL,
    [ID] [int] IDENTITY(1,1) NOT NULL,
    [Sex] [int] NOT NULL,
 CONSTRAINT [PK_Students] PRIMARY KEY CLUSTERED 
(
    [ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO
SET IDENTITY_INSERT [dbo].[Course] ON 

INSERT [dbo].[Course] ([ID], [CourseName]) VALUES (1, N'语文')
INSERT [dbo].[Course] ([ID], [CourseName]) VALUES (2, N'数学')
INSERT [dbo].[Course] ([ID], [CourseName]) VALUES (3, N'英语')
INSERT [dbo].[Course] ([ID], [CourseName]) VALUES (4, N'物理')
INSERT [dbo].[Course] ([ID], [CourseName]) VALUES (5, N'化学')
SET IDENTITY_INSERT [dbo].[Course] OFF
SET IDENTITY_INSERT [dbo].[ScoreAndCourse] ON 

INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (1, 1, 1, 65)
INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (1, 2, 2, 70)
INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (1, 3, 3, 80)
INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (1, 4, 4, 100)
INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (2, 1, 5, 80)
INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (2, 2, 6, 96)
INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (2, 3, 7, 55)
INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (2, 4, 8, 76)
INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (3, 1, 9, 75)
INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (3, 2, 10, 84)
INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (3, 3, 11, 69)
INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (3, 4, 12, 43)
INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (4, 1, 13, 72)
INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (4, 2, 14, 89)
INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (4, 3, 15, 65)
INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (4, 4, 16, 76)
INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (5, 1, 17, 88)
INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (5, 2, 18, 94)
INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (5, 3, 19, 82)
INSERT [dbo].[ScoreAndCourse] ([CourseID], [StudentID], [ID], [Number]) VALUES (5, 4, 20, 78)
SET IDENTITY_INSERT [dbo].[ScoreAndCourse] OFF
SET IDENTITY_INSERT [dbo].[Students] ON 

INSERT [dbo].[Students] ([Name], [ID], [Sex]) VALUES (N'张三', 1, 0)
INSERT [dbo].[Students] ([Name], [ID], [Sex]) VALUES (N'李四', 2, 0)
INSERT [dbo].[Students] ([Name], [ID], [Sex]) VALUES (N'王五', 3, 0)
INSERT [dbo].[Students] ([Name], [ID], [Sex]) VALUES (N'赵六', 4, 0)
SET IDENTITY_INSERT [dbo].[Students] OFF
USE [master]
GO
ALTER DATABASE [MyStudy] SET  READ_WRITE 
GO

对于列传行我们参考《T-SQL基础教程》中提供的方式

方法1：

WITH    CTE
          AS ( SELECT   tab3.Name ,
                        tab2.CourseName ,
                        tab1.Number
               FROM     dbo.ScoreAndCourse tab1
                        LEFT
JOIN dbo.Course tab2 ON tab2.ID = tab1.CourseID
                        LEFT JOIN dbo.Students tab3 ON tab3.ID = tab1.StudentID
             )
    SELECT  tab4.Name ,
            SUM(CASE WHEN tab4.CourseName = '语文' THEN tab4.Number
                END) AS '语文' ,
            SUM(CASE WHEN tab4.CourseName = '数学' THEN tab4.Number
                END) AS '数学' ,
            SUM(CASE WHEN tab4.CourseName = '英语' THEN tab4.Number
                END) AS '英语' ,
            SUM(CASE WHEN tab4.CourseName = '物理' THEN tab4.Number
                END) AS '物理' ,
            SUM(CASE WHEN tab4.CourseName = '化学' THEN tab4.Number
                END) AS '化学'
    FROM    CTE tab4
    GROUP BY tab4.Name
    ORDER BY tab4.Name;

方法2：

WITH    CTE
          AS ( SELECT   tab3.Name ,
                        tab2.CourseName ,
                        tab1.Number
               FROM     dbo.ScoreAndCourse tab1
                        LEFT
JOIN dbo.Course tab2 ON tab2.ID = tab1.CourseID
                        LEFT JOIN dbo.Students tab3 ON tab3.ID = tab1.StudentID
             )
    SELECT  p.Name ,
            语文 ,
            数学 ,
            英语 ,
            物理 ,
            化学
    FROM    CTE AS base1 PIVOT ( SUM(Number) FOR CourseName IN ( 语文, 数学, 英语,
                                                              物理, 化学 ) ) AS p;

注释：

1. CTE：公用表表达式

2.PIVOT：运算符（与之相反的 UNPIVOT ）