sql语句多表查询(学生表/课程表/教师表/成绩表 )

表结构：

1.学生表
Student(Sid,Sname,Sage,Ssex) --S# 学生编号,Sname 学生姓名,Sage 出生年月,Ssex 学生性别

2.课程表
Course(Cid,Cname,Tid) --C# --课程编号,Cname 课程名称,T# 教师编号

3.教师表
Teacher(Tid,Tname) --T# 教师编号,Tname 教师姓名

4.成绩表
SC(Scid,Cid,score) --S# 学生编号,C# 课程编号,score 分数

--创建测试数据
/*
Navicat MySQL Data Transfer
 
Source Server         : root
Source Server Version : 80022
Source Host           : localhost:3306
Source Database       : school
 
Target Server Type    : MYSQL
Target Server Version : 80022
File Encoding         : 65001
 
Date: 2022-03-30 17:14:07
*/
 
SET FOREIGN_KEY_CHECKS=0;
 
-- ----------------------------
-- Table structure for course
-- ----------------------------
DROP TABLE IF EXISTS `course`;
CREATE TABLE `course` (
  `Cid` varchar(10) DEFAULT NULL,
  `Cname` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL,
  `Tid` varchar(10) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
 
-- ----------------------------
-- Records of course
-- ----------------------------
INSERT INTO `course` VALUES ('01', '语文', '02');
INSERT INTO `course` VALUES ('02', '数学', '01');
INSERT INTO `course` VALUES ('03', '英语', '03');
 
-- ----------------------------
-- Table structure for sc
-- ----------------------------
DROP TABLE IF EXISTS `sc`;
CREATE TABLE `sc` (
  `Sid` varchar(10) DEFAULT NULL,
  `Cid` varchar(10) DEFAULT NULL,
  `score` decimal(18,1) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
 
-- ----------------------------
-- Records of sc
-- ----------------------------
INSERT INTO `sc` VALUES ('01', '01', '80.0');
INSERT INTO `sc` VALUES ('01', '02', '90.0');
INSERT INTO `sc` VALUES ('01', '03', '99.0');
INSERT INTO `sc` VALUES ('02', '01', '70.0');
INSERT INTO `sc` VALUES ('02', '02', '60.0');
INSERT INTO `sc` VALUES ('03', '01', '80.0');
INSERT INTO `sc` VALUES ('03', '02', '80.0');
INSERT INTO `sc` VALUES ('03', '03', '80.0');
INSERT INTO `sc` VALUES ('04', '01', '50.0');
INSERT INTO `sc` VALUES ('04', '02', '30.0');
INSERT INTO `sc` VALUES ('04', '03', '20.0');
INSERT INTO `sc` VALUES ('05', '01', '76.0');
INSERT INTO `sc` VALUES ('05', '02', '87.0');
INSERT INTO `sc` VALUES ('06', '01', '31.0');
INSERT INTO `sc` VALUES ('06', '03', '34.0');
INSERT INTO `sc` VALUES ('07', '02', '89.0');
INSERT INTO `sc` VALUES ('07', '03', '98.0');
 
-- ----------------------------
-- Table structure for student
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
  `Sid` varchar(10) DEFAULT NULL,
  `Sname` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL,
  `Sage` date DEFAULT NULL,
  `Ssex` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
 
-- ----------------------------
-- Records of student
-- ----------------------------
INSERT INTO `student` VALUES ('01', '赵雷', '1990-01-01', '男');
INSERT INTO `student` VALUES ('02', '钱电', '1990-12-21', '男');
INSERT INTO `student` VALUES ('03', '孙风', '1990-05-20', '男');
INSERT INTO `student` VALUES ('04', '李云', '1990-08-06', '男');
INSERT INTO `student` VALUES ('05', '周梅', '1991-12-01', '女');
INSERT INTO `student` VALUES ('06', '吴兰', '1992-03-01', '女');
INSERT INTO `student` VALUES ('07', '郑竹', '1989-07-01', '女');
INSERT INTO `student` VALUES ('08', '王菊', '1990-01-20', '女');
 
-- ----------------------------
-- Table structure for teacher
-- ----------------------------
DROP TABLE IF EXISTS `teacher`;
CREATE TABLE `teacher` (
  `Tid` varchar(10) DEFAULT NULL,
  `Tname` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
 
-- ----------------------------
-- Records of teacher
-- ----------------------------
INSERT INTO `teacher` VALUES ('01', '张三');
INSERT INTO `teacher` VALUES ('02', '李四');
INSERT INTO `teacher` VALUES ('03', '王五');

1、查询"01"课程比"02"课程成绩高的学生的信息及课程分数

1.1、查询同时存在"01"课程和"02"课程的情况

SELECT  a.* ,
        b.score 课程01的分数 ,
        c.score 课程02的分数
FROM    Student a ,
        SC b ,
        SC c
WHERE   a.Sid = b.Sid 
        AND a.Sid = c.Sid
        AND b.Cid = '01'
        AND c.Cid = '02'
        AND b.score > c.score

查询结果：

Sid	Sname	Sage	Ssex	课程01的分数	课程02的分数
 
02	钱电	1990-12-21	男	70.0	60.0
04	李云	1990-08-06	男	50.0	30.0

1.2、查询同时存在"01"课程和"02"课程的情况和存在"01"课程但可能不存在"02"课程的情况(不存在时显示为null)(以下存在相同内容时不再解释)

SELECT  a.* ,
        b.score 课程01的分数 ,
        c.score 课程02的分数
FROM    Student a
        LEFT JOIN SC b ON a.Sid  = b.Sid 
                          AND b.Cid  = '01'
        LEFT JOIN SC c ON a.Sid  = c.Sid 
                          AND c.Cid  = '02'
WHERE   b.score > ISNULL(c.score);

查询结果：

Sid	Sname	Sage	Ssex	课程01的分数	课程02的分数
 
01	赵雷	1990-01-01	男	80.0	90.0
02	钱电	1990-12-21	男	70.0	60.0
03	孙风	1990-05-20	男	80.0	80.0
04	李云	1990-08-06	男	50.0	30.0
05	周梅	1991-12-01	女	76.0	87.0
06	吴兰	1992-03-01	女	31.0

2、查询"01"课程比"02"课程成绩低的学生的信息及课程分数

2.1、查询同时存在"01"课程和"02"课程的情况

SELECT  a.* ,
        b.score 课程01的分数 ,
        c.score 课程02的分数
FROM    Student a ,
        SC b ,
        SC c
WHERE   a.Sid = b.Sid 
        AND a.Sid = c.Sid
        AND b.Cid = '01'
        AND c.Cid = '02'
        AND b.score < c.score

查询结果：

01	赵雷	1990-01-01	男	80.0	90.0
05	周梅	1991-12-01	女	76.0	87.0

3、查询平均成绩大于等于60分的同学的学生编号和学生姓名和平均成绩

SELECT  a.Sid ,
        a.Sname ,
        CAST(AVG(b.score) AS DECIMAL(18, 2)) avg_score
FROM    Student a ,
        sc b
WHERE   a.Sid = b.Sid
GROUP BY a.Sid ,
        a.Sname
HAVING  CAST(AVG(b.score) AS DECIMAL(18, 2)) >= 60
ORDER BY a.Sid

查询结果：

01	赵雷	89.67
02	钱电	65.00
03	孙风	80.00
05	周梅	81.50
07	郑竹	93.50

语法: CAST (expression AS data_type) 参数说明: expression:任何有效的SQServer表式。
SELECT CAST('12.5' AS decimal(9,2))
精度与小数位数分别为9 与2。
精度是总的数字位数，包括小数点左边和右边位数的总和。
而小数位数是小数点右边的位数。这表示本例能够支持的最大的整数值是9999999，而最小的小数是0.01。

4、查询平均成绩小于60分的同学的学生编号和学生姓名和平均成绩
4.1、查询在sc表存在成绩的学生信息的SQL语句。

SELECT  a.S# ,
        a.Sname ,
        CAST(AVG(b.score) AS DECIMAL(18, 2)) avg_score
FROM    Student a ,
        sc b
WHERE   a.S# = b.S#
GROUP BY a.S# ,
        a.Sname
HAVING  CAST(AVG(b.score) AS DECIMAL(18, 2)) < 60
ORDER BY a.S#

--4.2、查询在sc表中不存在成绩的学生信息的SQL语句。

SELECT  a.S# ,
        a.Sname ,
        ISNULL(CAST(AVG(b.score) AS DECIMAL(18, 2)), 0) avg_score
FROM    Student a
        LEFT JOIN sc b ON a.S# = b.S#
GROUP BY a.S# ,
        a.Sname
HAVING  ISNULL(CAST(AVG(b.score) AS DECIMAL(18, 2)), 0) < 60
ORDER BY a.S#

--5、查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩
--5.1、查询所有有成绩的SQL。

SELECT  a.S# [学生编号] ,
        a.Sname [学生姓名] ,
        COUNT(b.C#) 选课总数 ,
        SUM(score) [所有课程的总成绩]
FROM    Student a ,
        SC b
WHERE   a.S# = b.S#
GROUP BY a.S# ,
        a.Sname
ORDER BY a.S#

--5.2、查询所有(包括有成绩和无成绩)的SQL。

SELECT  a.S# [学生编号] ,
        a.Sname [学生姓名] ,
        COUNT(b.C#) 选课总数 ,
        SUM(score) [所有课程的总成绩]
FROM    Student a
        LEFT JOIN SC b ON a.S# = b.S#
GROUP BY a.S# ,
        a.Sname
ORDER BY a.S#

--6、查询"李"姓老师的数量

--方法1
SELECT  COUNT(Tname) ["李"姓老师的数量]
FROM    Teacher
WHERE   Tname LIKE N'李%'
--方法2
SELECT  COUNT(Tname) ["李"姓老师的数量]
FROM    Teacher
WHERE   LEFT(Tname, 1) = N'李'

--7、查询学过"张三"老师授课的同学的信息

SELECT DISTINCT
        Student.*
FROM    Student ,
        SC ,
        Course ,
        Teacher
WHERE   Student.S# = SC.S#
        AND SC.C# = Course.C#
        AND Course.T# = Teacher.T#
        AND Teacher.Tname = N'张三'
ORDER BY Student.S#

--8、查询没学过"张三"老师授课的同学的信息

SELECT  m.*
FROM    Student m
WHERE   S# NOT IN ( SELECT DISTINCT
                            SC.S#
                    FROM    SC ,
                            Course ,
                            Teacher
                    WHERE   SC.C# = Course.C#
                            AND Course.T# = Teacher.T#
                            AND Teacher.Tname = N'张三' )
ORDER BY m.S#

--9、查询学过编号为"01"并且也学过编号为"02"的课程的同学的信息

--方法1
SELECT  Student.*
FROM    Student ,
        SC
WHERE   Student.S# = SC.S#
        AND SC.C# = '01'
        AND EXISTS ( SELECT 1
                     FROM   SC SC_2
                     WHERE  SC_2.S# = SC.S#
                            AND SC_2.C# = '02' )
ORDER BY Student.S#
--方法2
SELECT  Student.*
FROM    Student ,
        SC
WHERE   Student.S# = SC.S#
        AND SC.C# = '02'
        AND EXISTS ( SELECT 1
                     FROM   SC SC_2
                     WHERE  SC_2.S# = SC.S#
                            AND SC_2.C# = '01' )
ORDER BY Student.S#
--方法3
SELECT  m.*
FROM    Student m
WHERE   S# IN ( SELECT  S#
                FROM    ( SELECT DISTINCT
                                    S#
                          FROM      SC
                          WHERE     C# = '01'
                          UNION ALL
                          SELECT DISTINCT
                                    S#
                          FROM      SC
                          WHERE     C# = '02'
                        ) t
                GROUP BY S#
                HAVING  COUNT(1) = 2 )
ORDER BY m.S#

--10、查询学过编号为"01"但是没有学过编号为"02"的课程的同学的信息

--方法1
SELECT  Student.*
FROM    Student ,
        SC
WHERE   Student.S# = SC.S#
        AND SC.C# = '01'
        AND NOT EXISTS ( SELECT 1
                         FROM   SC SC_2
                         WHERE  SC_2.S# = SC.S#
                                AND SC_2.C# = '02' )
ORDER BY Student.S#
--方法2
SELECT  Student.*
FROM    Student ,
        SC
WHERE   Student.S# = SC.S#
        AND SC.C# = '01'
        AND Student.S# NOT IN ( SELECT  SC_2.S#
                                FROM    SC SC_2
                                WHERE   SC_2.S# = SC.S#
                                        AND SC_2.C# = '02' )
ORDER BY Student.S#

--11、查询没有学全所有课程的同学的信息

--11.1、
SELECT  Student.*
FROM    Student ,
        SC
WHERE   Student.S# = SC.S#
GROUP BY Student.S# ,
        Student.Sname ,
        Student.Sage ,
        Student.Ssex
HAVING  COUNT(C#) < ( SELECT    COUNT(C#)
                      FROM      Course
                    )
--11.2
SELECT  Student.*
FROM    Student
        LEFT JOIN SC ON Student.S# = SC.S#
GROUP BY Student.S# ,
        Student.Sname ,
        Student.Sage ,
        Student.Ssex
HAVING  COUNT(C#) < ( SELECT    COUNT(C#)
                      FROM      Course
                    )

--12、查询至少有一门课与学号为"01"的同学所学相同的同学的信息

SELECT DISTINCT
        Student.*
FROM    Student ,
        SC
WHERE   Student.S# = SC.S#
        AND SC.C# IN ( SELECT   C#
                       FROM     SC
                       WHERE    S# = '01' )
        AND Student.S# <> '01'

--13、查询和"01"号的同学学习的课程完全相同的其他同学的信息

SELECT  Student.*
FROM    Student
WHERE   S# IN ( SELECT DISTINCT
                        SC.S#
                FROM    SC
                WHERE   S# <> '01'
                        AND SC.C# IN ( SELECT DISTINCT
                                                C#
                                       FROM     SC
                                       WHERE    S# = '01' )
                GROUP BY SC.S#
                HAVING  COUNT(1) = ( SELECT COUNT(1)
                                     FROM   SC
                                     WHERE  S# = '01'
                                   ) )

--14、查询没学过"张三"老师讲授的任一门课程的学生姓名

SELECT  student.*
FROM    student
WHERE   student.S# NOT IN ( SELECT DISTINCT
                                    sc.S#
                            FROM    sc ,
                                    course ,
                                    teacher
                            WHERE   sc.C# = course.C#
                                    AND course.T# = teacher.T#
                                    AND teacher.tname = N'张三' )
ORDER BY student.S#

--15、查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩

SELECT  student.S# ,
        student.sname ,
        CAST(AVG(score) AS DECIMAL(18, 2)) avg_score
FROM    student ,
        sc
WHERE   student.S# = SC.S#
        AND student.S# IN ( SELECT  S#
                            FROM    SC
                            WHERE   score < 60
                            GROUP BY S#
                            HAVING  COUNT(1) >= 2 )
GROUP BY student.S# ,
        student.sname

--16、检索"01"课程分数小于60，按分数降序排列的学生信息

SELECT  student.* ,
        sc.C# ,
        sc.score
FROM    student ,
        sc
WHERE   student.S# = SC.S#
        AND sc.score < 60
        AND sc.C# = '01'
ORDER BY sc.score DESC

--17、按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩

--17.1 SQL 2000 静态
SELECT  a.S# 学生编号 ,
        a.Sname 学生姓名 ,
        MAX(CASE c.Cname
              WHEN N'语文' THEN b.score
              ELSE NULL
            END) [语文] ,
        MAX(CASE c.Cname
              WHEN N'数学' THEN b.score
              ELSE NULL
            END) [数学] ,
        MAX(CASE c.Cname
              WHEN N'英语' THEN b.score
              ELSE NULL
            END) [英语] ,
        CAST(AVG(b.score) AS DECIMAL(18, 2)) 平均分
FROM    Student a
        LEFT JOIN SC b ON a.S# = b.S#
        LEFT JOIN Course c ON b.C# = c.C#
GROUP BY a.S# ,
        a.Sname
ORDER BY 平均分 DESC
--17.2 SQL 2000 动态
DECLARE @sql NVARCHAR(4000)
SET @sql = 'select a.S# ' + N'学生编号' + ' , a.Sname ' + N'学生姓名'
SELECT  @sql = @sql + ',max(case c.Cname when N''' + Cname
        + ''' then b.score else null end) [' + Cname + ']'
FROM    ( SELECT DISTINCT
                    Cname
          FROM      Course
        ) AS t
SET @sql = @sql + ' , cast(avg(b.score) as decimal(18,2)) ' + N'平均分'
    + ' from Student a left join SC b on a.S# = b.S# left join Course c on b.C# = c.C#
group by a.S# , a.Sname order by ' + N'平均分' + ' desc'
EXEC(@sql)
 
 
--24、查询学生平均成绩及其名次
--24.1 查询学生的平均成绩并进行排名，sql 2000用子查询完成，分平均成绩重复时保留名次空缺和不保留名次空缺两种。
SELECT  t1.* ,
        px = ( SELECT   COUNT(1)
               FROM     ( SELECT    m.S# [学生编号] ,
                                    m.Sname [学生姓名] ,
                                    ISNULL(CAST(AVG(score) AS DECIMAL(18, 2)),
                                           0) [平均成绩]
                          FROM      Student m
                                    LEFT JOIN SC n ON m.S# = n.S#
                          GROUP BY  m.S# ,
                                    m.Sname
                        ) t2
               WHERE    平均成绩 > t1.平均成绩
             ) + 1
FROM    ( SELECT    m.S# [学生编号] ,
                    m.Sname [学生姓名] ,
                    ISNULL(CAST(AVG(score) AS DECIMAL(18, 2)), 0) [平均成绩]
          FROM      Student m
                    LEFT JOIN SC n ON m.S# = n.S#
          GROUP BY  m.S# ,
                    m.Sname
        ) t1
ORDER BY px
 
SELECT  t1.* ,
        px = ( SELECT   COUNT(DISTINCT 平均成绩)
               FROM     ( SELECT    m.S# [学生编号] ,
                                    m.Sname [学生姓名] ,
                                    ISNULL(CAST(AVG(score) AS DECIMAL(18, 2)),
                                           0) [平均成绩]
                          FROM      Student m
                                    LEFT JOIN SC n ON m.S# = n.S#
                          GROUP BY  m.S# ,
                                    m.Sname
                        ) t2
               WHERE    平均成绩 >= t1.平均成绩
             )
FROM    ( SELECT    m.S# [学生编号] ,
                    m.Sname [学生姓名] ,
                    ISNULL(CAST(AVG(score) AS DECIMAL(18, 2)), 0) [平均成绩]
          FROM      Student m
                    LEFT JOIN SC n ON m.S# = n.S#
          GROUP BY  m.S# ,
                    m.Sname
        ) t1
ORDER BY px
--24.2 查询学生的平均成绩并进行排名，sql 2005用rank,DENSE_RANK完成，分平均成绩重复时保留名次空缺和不保留名次空缺两种。
SELECT  t.* ,
        px = RANK() OVER ( ORDER BY [平均成绩] DESC )
FROM    ( SELECT    m.S# [学生编号] ,
                    m.Sname [学生姓名] ,
                    ISNULL(CAST(AVG(score) AS DECIMAL(18, 2)), 0) [平均成绩]
          FROM      Student m
                    LEFT JOIN SC n ON m.S# = n.S#
          GROUP BY  m.S# ,
                    m.Sname
        ) t
ORDER BY px
 
SELECT  t.* ,
        px = DENSE_RANK() OVER ( ORDER BY [平均成绩] DESC )
FROM    ( SELECT    m.S# [学生编号] ,
                    m.Sname [学生姓名] ,
                    ISNULL(CAST(AVG(score) AS DECIMAL(18, 2)), 0) [平均成绩]
          FROM      Student m
                    LEFT JOIN SC n ON m.S# = n.S#
          GROUP BY  m.S# ,
                    m.Sname
        ) t
ORDER BY px
 
--25、查询各科成绩前三名的记录
--25.1 分数重复时保留名次空缺
SELECT  m.* ,
        n.C# ,
        n.score
FROM    Student m ,
        SC n
WHERE   m.S# = n.S#
        AND n.score IN ( SELECT TOP 3
                                score
                         FROM   sc
                         WHERE  C# = n.C#
                         ORDER BY score DESC )
ORDER BY n.C# ,
        n.score DESC
--25.2 分数重复时不保留名次空缺，合并名次
--sql 2000用子查询实现
SELECT  *
FROM    ( SELECT    t.* ,
                    px = ( SELECT   COUNT(DISTINCT score)
                           FROM     SC
                           WHERE    C# = t.C#
                                    AND score >= t.score
                         )
          FROM      sc t
        ) m
WHERE   px BETWEEN 1 AND 3
ORDER BY m.c# ,
        m.px
--sql 2005用DENSE_RANK实现
SELECT  *
FROM    ( SELECT    t.* ,
                    px = DENSE_RANK() OVER ( PARTITION BY c# ORDER BY score DESC )
          FROM      sc t
        ) m
WHERE   px BETWEEN 1 AND 3
ORDER BY m.C# ,
        m.px
 
--26、查询每门课程被选修的学生数
SELECT  c# ,
        COUNT(S#) [学生数]
FROM    sc
GROUP BY C#
 
--27、查询出只有两门课程的全部学生的学号和姓名
SELECT  Student.S# ,
        Student.Sname
FROM    Student ,
        SC
WHERE   Student.S# = SC.S#
GROUP BY Student.S# ,
        Student.Sname
HAVING  COUNT(SC.C#) = 2
ORDER BY Student.S#
 
--28、查询男生、女生人数
SELECT  COUNT(Ssex) AS 男生人数
FROM    Student
WHERE   Ssex = N'男'
SELECT  COUNT(Ssex) AS 女生人数
FROM    Student
WHERE   Ssex = N'女'
SELECT  SUM(CASE WHEN Ssex = N'男' THEN 1
                 ELSE 0
            END) [男生人数] ,
        SUM(CASE WHEN Ssex = N'女' THEN 1
                 ELSE 0
            END) [女生人数]
FROM    student
SELECT  CASE WHEN Ssex = N'男' THEN N'男生人数'
             ELSE N'女生人数'
        END [男女情况] ,
        COUNT(1) [人数]
FROM    student
GROUP BY CASE WHEN Ssex = N'男' THEN N'男生人数'
              ELSE N'女生人数'
         END
 
--29、查询名字中含有"风"字的学生信息
SELECT  *
FROM    student
WHERE   sname LIKE N'%风%'
SELECT  *
FROM    student
WHERE   CHARINDEX(N'风', sname) > 0
 
--30、查询同名同性学生名单，并统计同名人数
SELECT  Sname [学生姓名] ,
        COUNT(*) [人数]
FROM    Student
GROUP BY Sname
HAVING  COUNT(*) > 1
 
--31、查询1990年出生的学生名单(注：Student表中Sage列的类型是datetime)
SELECT  *
FROM    Student
WHERE   YEAR(sage) = 1990
SELECT  *
FROM    Student
WHERE   DATEDIFF(yy, sage, '1990-01-01') = 0
SELECT  *
FROM    Student
WHERE   DATEPART(yy, sage) = 1990
SELECT  *
FROM    Student
WHERE   CONVERT(VARCHAR(4), sage, 120) = '1990'
 
--32、查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩相同时，按课程编号升序排列
SELECT  m.C# ,
        m.Cname ,
        CAST(AVG(n.score) AS DECIMAL(18, 2)) avg_score
FROM    Course m ,
        SC n
WHERE   m.C# = n.C#
GROUP BY m.C# ,
        m.Cname
ORDER BY avg_score DESC ,
        m.C# ASC
 
--33、查询平均成绩大于等于85的所有学生的学号、姓名和平均成绩
SELECT  a.S# ,
        a.Sname ,
        CAST(AVG(b.score) AS DECIMAL(18, 2)) avg_score
FROM    Student a ,
        sc b
WHERE   a.S# = b.S#
GROUP BY a.S# ,
        a.Sname
HAVING  CAST(AVG(b.score) AS DECIMAL(18, 2)) >= 85
ORDER BY a.S#
 
--34、查询课程名称为"数学"，且分数低于60的学生姓名和分数
SELECT  sname ,
        score
FROM    Student ,
        SC ,
        Course
WHERE   SC.S# = Student.S#
        AND SC.C# = Course.C#
        AND Course.Cname = N'数学'
        AND score < 60
 
--35、查询所有学生的课程及分数情况；
SELECT  Student.* ,
        Course.Cname ,
        SC.C# ,
        SC.score
FROM    Student ,
        SC ,
        Course
WHERE   Student.S# = SC.S#
        AND SC.C# = Course.C#
ORDER BY Student.S# ,
        SC.C#
--36、查询任何一门课程成绩在70分以上的姓名、课程名称和分数；
SELECT  Student.* ,
        Course.Cname ,
        SC.C# ,
        SC.score
FROM    Student ,
        SC ,
        Course
WHERE   Student.S# = SC.S#
        AND SC.C# = Course.C#
        AND SC.score >= 70
ORDER BY Student.S# ,
        SC.C#
--37、查询不及格的课程
SELECT  Student.* ,
        Course.Cname ,
        SC.C# ,
        SC.score
FROM    Student ,
        SC ,
        Course
WHERE   Student.S# = SC.S#
        AND SC.C# = Course.C#
        AND SC.score < 60
ORDER BY Student.S# ,
        SC.C#
--38、查询课程编号为01且课程成绩在80分以上的学生的学号和姓名；
SELECT  Student.* ,
        Course.Cname ,
        SC.C# ,
        SC.score
FROM    Student ,
        SC ,
        Course
WHERE   Student.S# = SC.S#
        AND SC.C# = Course.C#
        AND SC.C# = '01'
        AND SC.score >= 80
ORDER BY Student.S# ,
        SC.C#
--39、求每门课程的学生人数
SELECT  Course.C# ,
        Course.Cname ,
        COUNT(*) [学生人数]
FROM    Course ,
        SC
WHERE   Course.C# = SC.C#
GROUP BY Course.C# ,
        Course.Cname
ORDER BY Course.C# ,
        Course.Cname
 
--40、查询选修"张三"老师所授课程的学生中，成绩最高的学生信息及其成绩
--40.1 当最高分只有一个时
SELECT TOP 1
        Student.* ,
        Course.Cname ,
        SC.C# ,
        SC.score
FROM    Student ,
        SC ,
        Course ,
        Teacher
WHERE   Student.S# = SC.S#
        AND SC.C# = Course.C#
        AND Course.T# = Teacher.T#
        AND Teacher.Tname = N'张三'
ORDER BY SC.score DESC
--40.2 当最高分出现多个时
SELECT  Student.* ,
        Course.Cname ,
        SC.C# ,
        SC.score
FROM    Student ,
        SC ,
        Course ,
        Teacher
WHERE   Student.S# = SC.S#
        AND SC.C# = Course.C#
        AND Course.T# = Teacher.T#
        AND Teacher.Tname = N'张三'
        AND SC.score = ( SELECT MAX(SC.score)
                         FROM   SC ,
                                Course ,
                                Teacher
                         WHERE  SC.C# = Course.C#
                                AND Course.T# = Teacher.T#
                                AND Teacher.Tname = N'张三'
                       )
 
--41、查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩
--方法1
SELECT  m.*
FROM    SC m ,
        ( SELECT    C# ,
                    score
          FROM      SC
          GROUP BY  C# ,
                    score
          HAVING    COUNT(1) > 1
        ) n
WHERE   m.C# = n.C#
        AND m.score = n.score
ORDER BY m.C# ,
        m.score ,
        m.S#
--方法2
SELECT  m.*
FROM    SC m
WHERE   EXISTS ( SELECT 1
                 FROM   ( SELECT    C# ,
                                    score
                          FROM      SC
                          GROUP BY  C# ,
                                    score
                          HAVING    COUNT(1) > 1
                        ) n
                 WHERE  m.C# = n.C#
                        AND m.score = n.score )
ORDER BY m.C# ,
        m.score ,
        m.S#
 
--42、查询每门功成绩最好的前两名
SELECT  t.*
FROM    sc t
WHERE   score IN ( SELECT TOP 2
                            score
                   FROM     sc
                   WHERE    C# = T.C#
                   ORDER BY score DESC )
ORDER BY t.C# ,
        t.score DESC
 
--43、统计每门课程的学生选修人数（超过5人的课程才统计）。要求输出课程号和选修人数，查询结果按人数降序排列，若人数相同，按课程号升序排列
SELECT  Course.C# ,
        Course.Cname ,
        COUNT(*) [学生人数]
FROM    Course ,
        SC
WHERE   Course.C# = SC.C#
GROUP BY Course.C# ,
        Course.Cname
HAVING  COUNT(*) >= 5
ORDER BY [学生人数] DESC ,
        Course.C#
 
--44、检索至少选修两门课程的学生学号
SELECT  student.S# ,
        student.Sname
FROM    student ,
        SC
WHERE   student.S# = SC.S#
GROUP BY student.S# ,
        student.Sname
HAVING  COUNT(1) >= 2
ORDER BY student.S#
 
--45、查询选修了全部课程的学生信息
--方法1 根据数量来完成
SELECT  student.*
FROM    student
WHERE   S# IN ( SELECT  S#
                FROM    sc
                GROUP BY S#
                HAVING  COUNT(1) = ( SELECT COUNT(1)
                                     FROM   course
                                   ) )
--方法2 使用双重否定来完成
SELECT  t.*
FROM    student t
WHERE   t.S# NOT IN ( SELECT DISTINCT
                                m.S#
                      FROM      ( SELECT    S# ,
                                            C#
                                  FROM      student ,
                                            course
                                ) m
                      WHERE     NOT EXISTS ( SELECT 1
                                             FROM   sc n
                                             WHERE  n.S# = m.S#
                                                    AND n.C# = m.C# ) )
--方法3 使用双重否定来完成
SELECT  t.*
FROM    student t
WHERE   NOT EXISTS ( SELECT 1
                     FROM   ( SELECT DISTINCT
                                        m.S#
                              FROM      ( SELECT    S# ,
                                                    C#
                                          FROM      student ,
                                                    course
                                        ) m
                              WHERE     NOT EXISTS ( SELECT 1
                                                     FROM   sc n
                                                     WHERE  n.S# = m.S#
                                                            AND n.C# = m.C# )
                            ) k
                     WHERE  k.S# = t.S# )
 
--46、查询各学生的年龄
--46.1 只按照年份来算
SELECT  * ,
        DATEDIFF(yy, sage, GETDATE()) [年龄]
FROM    student
--46.2 按照出生日期来算，当前月日 < 出生年月的月日则，年龄减一
SELECT  * ,
        CASE WHEN RIGHT(CONVERT(VARCHAR(10), GETDATE(), 120), 5) < RIGHT(CONVERT(VARCHAR(10), sage, 120),
                                                              5)
             THEN DATEDIFF(yy, sage, GETDATE()) - 1
             ELSE DATEDIFF(yy, sage, GETDATE())
        END [年龄]
FROM    student
 
--47、查询本周过生日的学生
SELECT  *
FROM    student
WHERE   DATEDIFF(week,
                 DATENAME(yy, GETDATE()) + RIGHT(CONVERT(VARCHAR(10), sage, 120),
                                                 6), GETDATE()) = 0
 
--48、查询下周过生日的学生
SELECT  *
FROM    student
WHERE   DATEDIFF(week,
                 DATENAME(yy, GETDATE()) + RIGHT(CONVERT(VARCHAR(10), sage, 120),
                                                 6), GETDATE()) = -1
 
--49、查询本月过生日的学生
SELECT  *
FROM    student
WHERE   DATEDIFF(mm,
                 DATENAME(yy, GETDATE()) + RIGHT(CONVERT(VARCHAR(10), sage, 120),
                                                 6), GETDATE()) = 0
 
--50、查询下月过生日的学生
SELECT  *
FROM    student
WHERE   DATEDIFF(mm,
                 DATENAME(yy, GETDATE()) + RIGHT(CONVERT(VARCHAR(10), sage, 120),
                                                 6), GETDATE()) = -1
 
DROP TABLE  Student,Course,Teacher,SC
posted @   Code7Rain  阅读(4710)  评论(0)  编辑  收藏  举报
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