USE master GO IF EXISTS(SELECT * FROM sysdatabases WHERE name='DB_StudentInfoManagement') DROP DATABASE DB_StudentInfoManagement GO CREATE DATABASE DB_StudentInfoManagement GO USE DB_StudentInfoManagement GO IF EXISTS(SELECT * FROM sysobjects WHERE name='Student') DROP TABLE Student GO CREATE TABLE Student ( S# INT PRIMARY KEY ,--学号 Sname NVARCHAR(100) NOT NULL,--姓名 Sage INT NOT NULL,--年龄 Ssex NVARCHAR(10) NOT NULL--性别 ) GO IF EXISTS(SELECT * FROM sysobjects WHERE name='Teacher') DROP TABLE Teacher GO CREATE TABLE Teacher ( T# INT PRIMARY KEY ,--教师编号 Tname NVARCHAR(50) NOT NULL,--教师名 ) GO IF EXISTS(SELECT * FROM sysobjects WHERE name='Course') DROP TABLE Course GO CREATE TABLE Course ( C# INT PRIMARY KEY ,--课程号 Cname NVARCHAR(50) NOT NULL,--课程名 T# INT NOT NULL REFERENCES Teacher(T#)--教师编号 ) GO IF EXISTS(SELECT * FROM sysobjects WHERE name='SC') DROP TABLE SC GO CREATE TABLE SC ( C# INT NOT NULL REFERENCES dbo.Course(C#),--课程号 S# INT NOT NULL REFERENCES dbo.Student(S#),--学号 Score NVARCHAR(50) NOT NULL,--分数 CONSTRAINT PK_SC PRIMARY KEY(C#,S#) )
--插入测试数据
INSERT INTO dbo.Student SELECT '1' , N'刘一' , '18' , N'男' UNION ALL --不会去除重复数据，Union会自动去除重复数据 SELECT '2' , N'钱二' , '19' , '女' UNION ALL SELECT '3' , N'张三' , '17' , N'男' UNION ALL SELECT '4' , N'李四' , '18' , N'女' UNION ALL SELECT '5' , N'王五' , '17' , N'男' UNION ALL SELECT '6' , N'赵六' , '19' , N'女'; INSERT INTO Teacher SELECT '1' , N'叶平' UNION ALL SELECT '2' , N'贺高' UNION ALL SELECT '3' , N'杨艳' UNION ALL SELECT '4' , N'周磊'; INSERT INTO Course SELECT '1' , N'语文' , '1' UNION ALL SELECT '2' , N'数学' , '2' UNION ALL SELECT '3' , N'英语' , '3' UNION ALL SELECT '4' , N'物理' , '4'; INSERT INTO SC SELECT 1 , 1 , 56 UNION ALL SELECT 1 , 2 , 78 UNION ALL SELECT 1 , 3 , 67 UNION ALL SELECT 1 , 4 , 58 UNION ALL SELECT 2 , 1 , 79 UNION ALL SELECT 2 , 2 , 81 UNION ALL SELECT 2 , 3 , 92 UNION ALL SELECT 2 , 4 , 68 UNION ALL SELECT 3 , 1 , 91 UNION ALL SELECT 3 , 2 , 47 UNION ALL SELECT 3 , 3 , 88 UNION ALL SELECT 3 , 4 , 56 UNION ALL SELECT 4 , 2 , 88 UNION ALL SELECT 4 , 3 , 90 UNION ALL SELECT 4 , 4 , 93 UNION ALL SELECT 5 , 1 , 46 UNION ALL SELECT 5 , 3 , 78 UNION ALL SELECT 5 , 4 , 53 UNION ALL SELECT 6 , 1 , 35 UNION ALL SELECT 6 , 2 , 68 UNION ALL SELECT 6 , 4 , 71;
--1、查询“001”课程比“002”课程成绩高的所有学生的学号； --先查出001号，002号课程的学号和成绩 --在使用子查询连表查询 SELECT a.S# FROM ( SELECT S# , Score FROM dbo.SC WHERE C# = '001' ) AS a , --001号课程的学号和成绩 ( SELECT S# , Score FROM dbo.SC WHERE C# = '002' ) AS b ----002号课程的学号和成绩 WHERE a.S# = b.S# AND a.Score > b.Score;
验证：
SELECT S# ,
Score
FROM dbo.SC
WHERE C# = '001'
SELECT S# ,
Score
FROM dbo.SC
WHERE C# = '002'
--2、查询平均成绩大于60分的同学的学号和平均成绩； --Having子句中，不能使用聚合函数的别名【错误答案：列名 'AvgScore' 无效。】 SELECT S#,AVG(Score)AS AvgScore FROM dbo.SC GROUP BY S# HAVING AvgScore>60
--正确答案： SELECT S#,AVG(Score)AS AvgScore FROM dbo.SC GROUP BY S# HAVING AVG(Score)>60
--3、查询所有同学的学号、姓名、选课数、总成绩； --这里要注意的是，并不是所有学生都选课了，所以要用到外连接， --因为是要查询所有学生的学号，姓名，，也就是不管该学生，选没选课，都要查出来，所以左表是Student，用左连接 SELECT S.S# , S.Sname , COUNT(SC.C#) AS SelectCourseCount , SUM(SC.Score) AS TotalScore FROM dbo.Student AS S LEFT JOIN dbo.SC AS SC ON SC.S# = S.S# GROUP BY S.S#,S.Sname;
--4、查询姓“李”的老师的个数； --分析，用到模糊查询,只要姓李就行，后面几个字的名，不管 --'%代表任意字符的字符串，_代表单个字符' --同名的也算，这是明显的。网上的答案是错误的。 --自己的答案 SELECT COUNT(T#) FROM dbo.Teacher WHERE Tname LIKE '李%'; --网上的答案：同名的也算，网上的答案是错误的了 SELECT COUNT(DISTINCT ( Tname )) FROM Teacher WHERE Tname LIKE '李%';
验证：
--测试
--SELECT * FROM dbo.Teacher WHERE Tname LIKE '李%';
--5、查询没学过“叶平”老师课的同学的学号、姓名； --分析：先查出学过叶平老师课的学生学号，再求出Student表中学号不在这其中的就是了 SELECT S#,Sname FROM dbo.Student WHERE S# NOT IN ( --学过叶平老师课的学生学号 SELECT DISTINCT( SC.S#) FROM dbo.Course AS C INNER JOIN dbo.Teacher AS T ON T.T# = C.T# INNER JOIN dbo.SC AS SC ON SC.C# = C.C# WHERE T.Tname='叶平' )
--6、查询学过“001”并且也学过编号“002”课程的同学的学号、姓名； --查出学过001号课程的 SELECT s.S# , Sname FROM dbo.Student AS s RIGHT JOIN dbo.SC ON SC.S# = s.S# WHERE C# = '001' AND EXISTS ( SELECT * FROM SC AS SC2 LEFT JOIN dbo.Student AS s ON s.S# = SC2.S# WHERE SC2.C# = '002' );
未完待整理...........