select * from 后有多个表的使用方法(已知一个表的结构为xxx 怎样通过select语句把他变成以下结构)

Posted 2020-11-24 shiyusdream

已知一个表的结构为：

 

 怎样通过select语句把他变成以下结构：

 

 

首先，添加数据

USE [DBTEST]
GO
/****** Object: Table [dbo].[SDUDENTS] Script Date: 2019/12/9 10:33:41 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[SDUDENTS](
[GUID] [int] IDENTITY(100001,1) NOT NULL,
[STUDENT] [nvarchar](50) NOT NULL,
[KEMU] [nvarchar](50) NULL,
[CHENGJI] [int] NULL,
CONSTRAINT [PK_SDUDENTS_1] PRIMARY KEY CLUSTERED
(
[GUID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY]
GO
SET IDENTITY_INSERT [dbo].[SDUDENTS] ON
GO
INSERT [dbo].[SDUDENTS] ([GUID], [STUDENT], [KEMU], [CHENGJI]) VALUES (100001, N‘李四‘, N‘语文‘, 75)
GO
INSERT [dbo].[SDUDENTS] ([GUID], [STUDENT], [KEMU], [CHENGJI]) VALUES (100002, N‘马六‘, N‘语文‘, 89)
GO
INSERT [dbo].[SDUDENTS] ([GUID], [STUDENT], [KEMU], [CHENGJI]) VALUES (100003, N‘王五‘, N‘语文‘, 67)
GO
INSERT [dbo].[SDUDENTS] ([GUID], [STUDENT], [KEMU], [CHENGJI]) VALUES (100004, N‘张三‘, N‘语文‘, 60)
GO
INSERT [dbo].[SDUDENTS] ([GUID], [STUDENT], [KEMU], [CHENGJI]) VALUES (100005, N‘张三‘, N‘数学‘, 34)
GO
INSERT [dbo].[SDUDENTS] ([GUID], [STUDENT], [KEMU], [CHENGJI]) VALUES (100006, N‘李四‘, N‘数学‘, 79)
GO
INSERT [dbo].[SDUDENTS] ([GUID], [STUDENT], [KEMU], [CHENGJI]) VALUES (100007, N‘王五‘, N‘数学‘, 98)
GO
INSERT [dbo].[SDUDENTS] ([GUID], [STUDENT], [KEMU], [CHENGJI]) VALUES (100008, N‘马六‘, N‘数学‘, 78)
GO
INSERT [dbo].[SDUDENTS] ([GUID], [STUDENT], [KEMU], [CHENGJI]) VALUES (100009, N‘张三‘, N‘英语‘, 88)
GO
INSERT [dbo].[SDUDENTS] ([GUID], [STUDENT], [KEMU], [CHENGJI]) VALUES (100010, N‘李四‘, N‘英语‘, 87)
GO
INSERT [dbo].[SDUDENTS] ([GUID], [STUDENT], [KEMU], [CHENGJI]) VALUES (100011, N‘王五‘, N‘英语‘, 99)
GO
INSERT [dbo].[SDUDENTS] ([GUID], [STUDENT], [KEMU], [CHENGJI]) VALUES (100012, N‘马六‘, N‘英语‘, 54)
GO
SET IDENTITY_INSERT [dbo].[SDUDENTS] OFF
GO

 

1.先将这个表互相连接查询（需要几个科目就连几次，我这儿有三个科目，所以连3次，SDUDENTS A,SDUDENTS B,SDUDENTS C）

select * from SDUDENTS A,SDUDENTS B,SDUDENTS C

得到以下数据（12*12*12      1728条数据）

 

 2.对表数据进行学生姓名筛选

select * from SDUDENTS A,SDUDENTS B,SDUDENTS C where a.STUDENT=b.STUDENT AND b.STUDENT=c.STUDENT

得到如下数据

 

 3.对科目进行筛选

select * from SDUDENTS A,SDUDENTS B,SDUDENTS C where a.STUDENT=b.STUDENT AND b.STUDENT=c.STUDENT
AND A.KEMU=‘语文‘ AND B.KEMU=‘数学‘ AND C.KEMU=‘英语‘;

得到以下数据

 

 4.定义好查询的内容

select A.STUDENT AS 学生,A.CHENGJI AS 语文,B.CHENGJI AS 数学,C.CHENGJI AS 英语 from SDUDENTS A,SDUDENTS B,SDUDENTS C
where a.STUDENT=b.STUDENT AND b.STUDENT=c.STUDENT
AND A.KEMU=‘语文‘ AND B.KEMU=‘数学‘ AND C.KEMU=‘英语‘;

得到以下数据

 

 新人小白一枚，如果有什么不对的地方望各位大佬多多指点