数据库基础SQL知识面试题二

　　　　　　　　　　　　　数据库基础SQL知识面试题二

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　作者：尹正杰

一.选课系统SQL语法练习

course数据库中有以下四张表：

•students表（学生表）：

　　　　sid整型自增主键，sname字符串64位，gender字符串12位，dept_id整型并外键到dept表的id字段。

  •dept表（系表）：

　　　　id整型自增主键，dept_name字符串64位。

  •course表（课程表）：

　　　　id整型自增字段主键，course_name字符串64位，teacher_id整型外键到teacher表的id字段。

  •teacher表（老师表）：

　　　　id整型自增字段主键，name字符串64位，dept_id整型外键到dept表的id字段。

  •score表（选课成绩表）：

        sid整型自增主键，course_id整型，score整型。

各表的预置数据如下所示：

• students表:

　　(,’Jason Yin’,,),(,’Andy’,,),(,’Bob’,,),(,’Ruth’,,),(,’Mike’,,),(,’John’, ,),(,’Cindy’,,),(,’Susan’,,)

• dept表:

　　(,’Education’),(,’Computer Science’),(,’Mathematics’)

• course表:

　　(,‘math’,),(,’english’,),(,’chinese’,),(,’history’,),(,’biology’,)

• teacher表:

　　(,’Zhang san’,),(,’Li si’,),(,’Wang wu’,),(,’Liu liu’,),(,’Ding qi’,)

• score表:

　　(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(, ,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,)

1>.请根据上述的信息创建出相应的表和插入预置数据

mysql> CREATE DATABASE course CHARACTER SET = utf8;

Query OK,  row affected,  warning (0.00 sec)

mysql>

mysql> USE course;

Database changed

mysql>

mysql> SELECT DATABASE();

+------------+

| DATABASE() |

+------------+

| course     |

+------------+

row in set (0.00 sec)

mysql>

mysql> CREATE TABLE dept(id INT PRIMARY KEY AUTO_INCREMENT,demt_name VARCHAR());

Query OK,  rows affected (0.01 sec)

mysql>

mysql> CREATE TABLE students(

    ->  sid INT PRIMARY KEY AUTO_INCREMENT,

    ->  sname VARCHAR(),

    ->  gender VARCHAR(),

    ->  dept_id INT NOT NULL,

    ->  CONSTRAINT student_dept FOREIGN KEY(dept_id) REFERENCES dept(id)

    -> );

Query OK,  rows affected (0.02 sec)

mysql>

mysql>

mysql> CREATE TABLE teacher(

    ->  id INT PRIMARY KEY AUTO_INCREMENT,

    ->  name VARCHAR(),

    ->  dept_id INT NOT NULL,

    ->  CONSTRAINT teacher_dept FOREIGN KEY(dept_id) REFERENCES dept(id)

    -> );

Query OK,  rows affected (0.01 sec)

mysql>

mysql> CREATE TABLE course(

    ->  id INT PRIMARY KEY AUTO_INCREMENT,

    ->  course_name VARCHAR(),

    ->  teacher_id INT,

    ->  CONSTRAINT course_teacher FOREIGN KEY(teacher_id) REFERENCES teacher(id)

    -> );

Query OK,  rows affected (0.01 sec)

mysql>

mysql> CREATE TABLE score(sid INT,course_id INT,score INT,PRIMARY KEY(sid,course_id));

Query OK,  rows affected (0.01 sec)

mysql>

创建数据库与对应的表结构

mysql> INSERT INTO dept VALUES(,'Education'),(,'Computer Science'),(,'Mathematics');

Query OK,  rows affected (0.01 sec)

Records:   Duplicates:   Warnings: 

mysql>

mysql> INSERT INTO teacher VALUES(,'Zhang san',),(,'Li si',),(,'Wang wu',),(,'Liu liu',),(,'Ding qi',);

Query OK,  rows affected (0.00 sec)

Records:   Duplicates:   Warnings: 

mysql>

mysql> INSERT INTO students VALUES(,'Jason Yin',,),(,'Andy',,),(,'Bob',,),(,'Ruth',,),(,'Mike',,),(,'John',,),(,'Cindy',,),(,'Susan',,);

Query OK,  rows affected (0.00 sec)

Records:   Duplicates:   Warnings: 

mysql>

mysql> INSERT INTO course VALUES(,'math',),(,'english',),(,'chinese',),(,'history',),(,'biology',);

Query OK,  rows affected (0.00 sec)

Records:   Duplicates:   Warnings: 

mysql>

mysql> INSERT INTO score VALUES(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,),(,,);

Query OK,  rows affected (0.01 sec)

Records:   Duplicates:   Warnings: 

mysql>

mysql>

插入预置数据

2>.查看所有英语成绩超过数学成绩的学生的学号和姓名

mysql> SELECT aa.sid,aa.sname FROM (SELECT a1.sid,sname,score FROM students a1 INNER JOIN score b1 ON a1.sid=b1.sid WHERE course_id=) aa INNER JOIN  (SELECT a2.sid,sname, score FROM students a2 INNER JOIN score b2 ON a2.sid=b2.sid WHERE course_id=) bb ON aa.sid=bb.sid WHERE aa.score>bb.score;

+-----+-----------+

| sid | sname     |

+-----+-----------+

|    | Jason Yin |

|    | Bob       |

|    | Cindy     |

+-----+-----------+

 rows in set (0.00 sec)

mysql>

mysql>

mysql> SELECT aa.sid,aa.sname FROM (SELECT a1.sid,sname,score FROM students a1 INNER JOIN score b1 ON a1.sid=b1.sid WHERE course_id=2) aa INNER JOIN (SELECT a2.sid,sname, score FROM students a2 INNER JOIN score b2 ON a2.sid=b2.sid WHERE course_id=1) bb ON aa.sid=bb.sid WHERE aa.score>bb.score;

3>.查看平均成绩大于等于60的所有学生的姓名和平均成绩

mysql> SELECT a.sid,a.sname,AVG(b.score) FROM students a INNER JOIN  score b ON a.sid=b.sid GROUP BY  a.sid,a.sname HAVING AVG(b.score)>=;

+-----+-----------+--------------+

| sid | sname     | AVG(b.score) |

+-----+-----------+--------------+

|    | Jason Yin |      76.0000 |

|    | Andy      |      78.0000 |

|    | Bob       |      79.8000 |

|    | Ruth      |      72.5000 |

|    | Mike      |      82.3333 |

|    | John      |      73.0000 |

|    | Cindy     |      64.2000 |

|    | Susan     |      94.0000 |

+-----+-----------+--------------+

 rows in set (0.00 sec)

mysql>

mysql>

mysql> SELECT a.sid,a.sname,AVG(b.score) FROM students a INNER JOIN score b ON a.sid=b.sid GROUP BY a.sid,a.sname HAVING AVG(b.score)>=60;

4>.查询所有同学的学号，姓名，选课数和总成绩

mysql> SELECT a.sid,a.sname,COUNT(*),SUM(score) FROM students a INNER JOIN score b ON a.sid=b.sid GROUP BY a.sid,a.sname;

+-----+-----------+----------+------------+

| sid | sname     | COUNT(*) | SUM(score) |

+-----+-----------+----------+------------+

|    | Jason Yin |         |         |

|    | Andy      |         |         |

|    | Bob       |         |         |

|    | Ruth      |         |         |

|    | Mike      |         |         |

|    | John      |         |         |

|    | Cindy     |         |         |

|    | Susan     |         |         |

+-----+-----------+----------+------------+

 rows in set (0.00 sec)

mysql>

mysql>

mysql> SELECT a.sid,a.sname,COUNT(*),SUM(score) FROM students a INNER JOIN score b ON a.sid=b.sid GROUP BY a.sid,a.sname;

5>.查询姓zhang的老师的个数

mysql> SELECT count(*) FROM teacher WHERE name LIKE 'zhang%';

+----------+

| count(*) |

+----------+

|         |

+----------+

 row in set (0.00 sec)

mysql>

mysql>

mysql> SELECT count(*) FROM teacher WHERE name LIKE 'zhang%';

6>.查询没学过zhangsan老师课程的学生的学号和姓名

mysql> SELECT sid,sname FROM students WHERE Sid NOT IN (SELECT b.sid FROM course a INNER JOIN score b ON a.id=b.course_id INNER JOIN teacher c ON a.teacher_id=c.id WHERE c.name='Zhang san');

+-----+-----------+

| sid | sname     |

+-----+-----------+

|    | Jason Yin |

+-----+-----------+

 row in set (0.00 sec)

mysql>

mysql> SELECT sid,sname FROM students WHERE Sid NOT IN (SELECT b.sid FROM course a INNER JOIN score b ON a.id=b.course_id INNER JOIN teacher c ON a.teacher_id=c.id WHERE c.name='Zhang san');

7>.查询既学过英语也学过语文的学生的学号和姓名

mysql> SELECT a.sid,sname,count(*) FROM students a INNER JOIN score b ON a.sid=b.sid INNER JOIN course c ON b.course_id=c.id AND c.course_name in ('english', 'chinese') GROUP BY  Sid,sname HAVING COUNT(*)>=;

+-----+-----------+----------+

| sid | sname     | count(*) |

+-----+-----------+----------+

|    | Jason Yin |         |

|    | Andy      |         |

|    | Bob       |         |

|    | Cindy     |         |

+-----+-----------+----------+

 rows in set (0.00 sec)

mysql>

mysql> SELECT a.sid,sname,count(*) FROM students a INNER JOIN score b ON a.sid=b.sid INNER JOIN course c ON b.course_id=c.id AND c.course_name in ('english', 'chinese') GROUP BY Sid,sname HAVING COUNT(*)>=2;

8>.查询有学生的单科成绩小于60的姓名和课程名称

mysql>

mysql> SELECT a.sname,c.course_name FROM students a INNER JOIN score b ON a.sid=b.sid INNER JOIN course c ON b.course_id=c.id WHERE b.score<;

+-----------+-------------+

| sname     | course_name |

+-----------+-------------+

| Jason Yin | biology     |

| Bob       | math        |

| John      | english     |

| Cindy     | math        |

+-----------+-------------+

 rows in set (0.01 sec)

mysql>

mysql>

mysql> SELECT a.sname,c.course_name FROM students a INNER JOIN score b ON a.sid=b.sid INNER JOIN course c ON b.course_id=c.id WHERE b.score<60;

9>.按平均成绩从高到低显示所有学生的姓名和语文，数学，英语三科成绩

mysql> SELECT a.sid,AVG(score) score_avg,SUM(CASE WHEN b.course_name='chinese' THEN a.score ELSE  END) a1,SUM(CASE WHEN b.course_name='math' THEN a.score ELSE  END) a2,SUM(CASE WHEN b.course_name='English' THEN a.score ELSE  END) a3  FROM score a INNER JOIN course b ON a.course_id=b.id  GROUP BY a.sid;

+-----+-----------+------+------+------+

| sid | score_avg | a1   | a2   | a3   |

+-----+-----------+------+------+------+

|    |   76.0000 |    |    |    |

|    |   78.0000 |    |     |    |

|    |   79.8000 |    |    |    |

|    |   72.5000 |    |     |     |

|    |   82.3333 |    |    |     |

|    |   73.0000 |     |     |    |

|    |   64.2000 |    |    |    |

|    |   94.0000 |     |     |     |

+-----+-----------+------+------+------+

 rows in set (0.00 sec)

mysql>

mysql> SELECT a.sid,AVG(score) score_avg,SUM(CASE WHEN b.course_name='chinese' THEN a.score ELSE 0 END) a1,SUM(CASE WHEN b.course_name='math' THEN a.score ELSE 0 END) a2,SUM(CASE WHEN b.course_name='English' THEN a.score ELSE 0 END) a3 FROM score a INNER JOIN course b ON a.course_id=b.id GROUP BY a.sid;

10>.查询各科成绩中的最高分和最低分

mysql> SELECT course_id,MIN(score),MAX(score) FROM score GROUP BY course_id;

+-----------+------------+------------+

| course_id | MIN(score) | MAX(score) |

+-----------+------------+------------+

|          |          |          |

|          |          |          |

|          |          |          |

|          |          |         |

|          |          |          |

+-----------+------------+------------+

 rows in set (0.00 sec)

mysql>

mysql>

mysql> SELECT course_id,MIN(score),MAX(score) FROM score GROUP BY course_id;

11>.计算各科平均成绩和及格率百分比

mysql> SELECT course_id,AVG(score),SUM(CASE WHEN score>= THEN  ELSE  END)/COUNT(*)* FROM score GROUP BY course_id;

+-----------+------------+---------------------------------------------------------+

| course_id | AVG(score) | SUM(CASE WHEN score>= THEN  ELSE  END)/COUNT(*)* |

+-----------+------------+---------------------------------------------------------+

|          |    63.5000 |                                                 50.0000 |

|          |    77.2000 |                                                 80.0000 |

|          |    77.5000 |                                                100.0000 |

|          |    76.6000 |                                                 80.0000 |

|          |    82.0000 |                                                100.0000 |

+-----------+------------+---------------------------------------------------------+

 rows in set (0.00 sec)

mysql>

mysql>

mysql> SELECT course_id,AVG(score),SUM(CASE WHEN score>=60 THEN 1 ELSE 0 END)/COUNT(*)*100 FROM score GROUP BY course_id;

12>.查询不同老师所教不同课程平均分从高到低

mysql> SELECT c.name,b.course_name,AVG(score) FROM score a INNER JOIN course b ON a.course_id=b.id INNER JOIN teacher c ON b.teacher_id=c.id GROUP BY c.name,b.course_name ORDER BY AVG(score) DESC;

+-----------+-------------+------------+

| name      | course_name | AVG(score) |

+-----------+-------------+------------+

| Zhang san | history     |    82.0000 |

| Liu liu   | chinese     |    77.5000 |

| Li si     | english     |    77.2000 |

| Ding qi   | biology     |    76.6000 |

| Wang wu   | math        |    63.5000 |

+-----------+-------------+------------+

 rows in set (0.00 sec)

mysql>

mysql> SELECT c.name,b.course_name,AVG(score) FROM score a INNER JOIN course b ON a.course_id=b.id INNER JOIN teacher c ON b.teacher_id=c.id GROUP BY c.name,b.course_name ORDER BY AVG(score) DESC;

13>.查询英语和数学课程成绩排名第5到第10位的学生姓名和成绩

mysql> SELECT c.sname,a.score FROM score a INNER JOIN course b ON a.course_id=b.id INNER JOIN students c ON a.sid=c.sid WHERE b.course_name='English' ORDER BY a.score LIMIT ,;

+-------+-------+

| sname | score |

+-------+-------+

| Bob   |     |

+-------+-------+

 row in set (0.00 sec)

mysql>

mysql>

mysql> SELECT c.sname,a.score FROM score a INNER JOIN course b ON a.course_id=b.id INNER JOIN students c ON a.sid=c.sid WHERE b.course_name='English' ORDER BY a.score LIMIT 4,6;

14>.统计按照各科成绩，分段统计每个课程在90分以上、80-90的、60~80、低于60分的人数

mysql> SELECT b.course_name,SUM(CASE WHEN score>= THEN  ELSE  END),SUM(CASE WHEN score< AND score>= THEN  ELSE  END),SUM(CASE WHEN score< AND score>= THEN  ELSE  END),SUM(CASE WHEN score< THEN  ELSE  END) FROM score a INNER JOIN course b ON a.course_id=b.id GROUP BY b.course_name;

+-------------+--------------------------------------------+---------------------------------------------------------+---------------------------------------------------------+-------------------------------------------+

| course_name | SUM(CASE WHEN score>= THEN  ELSE  END) | SUM(CASE WHEN score< AND score>= THEN  ELSE  END) | SUM(CASE WHEN score< AND score>= THEN  ELSE  END) | SUM(CASE WHEN score< THEN  ELSE  END) |

+-------------+--------------------------------------------+---------------------------------------------------------+---------------------------------------------------------+-------------------------------------------+

| math        |                                           |                                                        |                                                        |                                          |

| english     |                                           |                                                        |                                                        |                                          |

| chinese     |                                           |                                                        |                                                        |                                          |

| biology     |                                           |                                                        |                                                        |                                          |

| history     |                                           |                                                        |                                                        |                                          |

+-------------+--------------------------------------------+---------------------------------------------------------+---------------------------------------------------------+-------------------------------------------+

 rows in set (0.00 sec)

mysql>

mysql>

mysql> SELECT b.course_name,SUM(CASE WHEN score>=90 THEN 1 ELSE 0 END),SUM(CASE WHEN score=80 THEN 1 ELSE 0 END),SUM(CASE WHEN score=60 THEN 1 ELSE 0 END),SUM(CASE WHEN score

15>.查看每门课程被选修的学生数

mysql> SELECT course_id,COUNT(*) FROM score GROUP BY course_id;

+-----------+----------+

| course_id | COUNT(*) |

+-----------+----------+

|          |         |

|          |         |

|          |         |

|          |         |

|          |         |

+-----------+----------+

 rows in set (0.00 sec)

mysql>

mysql>

mysql> SELECT course_id,COUNT(*) FROM score GROUP BY course_id;

16>.查看只学习了一门课程的学生的姓名和学号

mysql> SELECT course_id,COUNT(*) FROM score GROUP BY course_id;

+-----------+----------+

| course_id | COUNT(*) |

+-----------+----------+

|          |         |

|          |         |

|          |         |

|          |         |

|          |         |

+-----------+----------+

 rows in set (0.00 sec)

mysql>

mysql>

mysql> SELECT course_id,COUNT(*) FROM score GROUP BY course_id;

17>.查询名字相同的学生名单和个数

mysql> SELECT sname,count(*) FROM students GROUP BY sname HAVING COUNT(*)>=;

Empty set (0.00 sec)

mysql>

mysql> SELECT sname,count(*) FROM students GROUP BY sname HAVING COUNT(*)>=2;

18>.85年之后出生的学生人数

mysql> alter table students add brithday datetime;

Query OK,  rows affected (0.01 sec)

Records:   Duplicates:   Warnings: 

mysql> update students set brithday='1983-01-01' where sid<;

Query OK,  rows affected (0.01 sec)

Rows matched:   Changed:   Warnings: 

mysql> update students set brithday='1986-01-01' where sid>=;

Query OK,  rows affected (0.01 sec)

Rows matched:   Changed:   Warnings: 

mysql>

添加字段并插入测试数据

mysql>  SELECT * FROM students WHERE brithday>='1985-01-01';

+-----+-------+--------+---------+---------------------+

| sid | sname | gender | dept_id | brithday            |

+-----+-------+--------+---------+---------------------+

|    | Mike  |       |        | -- :: |

|    | John  |       |        | -- :: |

|    | Cindy |       |        | -- :: |

|    | Susan |       |        | -- :: |

+-----+-------+--------+---------+---------------------+

 rows in set (0.00 sec)

mysql>

mysql>

mysql> SELECT * FROM students WHERE brithday>='1985-01-01';

19>.查询每门课程的平均成绩，按升序排序，如果平均成绩相同按ID降序排序

mysql> SELECT course_id,AVG(score) FROM score GROUP BY course_id ORDER BY AVG(score),course_id DESC;

+-----------+------------+

| course_id | AVG(score) |

+-----------+------------+

|          |    63.5000 |

|          |    76.6000 |

|          |    77.2000 |

|          |    77.5000 |

|          |    82.0000 |

+-----------+------------+

 rows in set (0.00 sec)

mysql>

mysql>

mysql> SELECT course_id,AVG(score) FROM score GROUP BY course_id ORDER BY AVG(score),course_id DESC;

20>.查询有不及格学生的课程和不及格学生个数

mysql> SELECT  course_id,COUNT(*) FROM score WHERE score< GROUP BY course_id;

+-----------+----------+

| course_id | COUNT(*) |

+-----------+----------+

|          |         |

|          |         |

|          |         |

+-----------+----------+

 rows in set (0.00 sec)

mysql>

mysql>

mysql> SELECT course_id,COUNT(*) FROM score WHERE score

21>.将所有学生姓名中前后的空格去掉

mysql> UPDATE students SET sname=LTRIM(RTRIM(sname));

Query OK,  rows affected (0.01 sec)

Rows matched:   Changed:   Warnings: 

mysql>

mysql>

mysql> UPDATE students SET sname=LTRIM(RTRIM(sname));

22>.将所有学生的考试成绩展示为课程名:成绩样式

mysql>

mysql> SELECT a.sid,CONCAT(b.course_name,':',a.score)FROM score a INNER  JOIN course b ON a.course_id=b.id;

+-----+-----------------------------------+

| sid | CONCAT(b.course_name,':',a.score) |

+-----+-----------------------------------+

|    | math:                           |

|    | english:                        |

|    | chinese:                        |

|    | biology:                        |

|    | english:                        |

|    | chinese:                        |

|    | history:                        |

|    | biology:                        |

|    | math:                           |

|    | english:                        |

|    | chinese:                        |

|    | history:                        |

|    | biology:                        |

|    | chinese:                        |

|    | history:                        |

|    | math:                           |

|    | chinese:                        |

|    | history:                        |

|    | english:                        |

|    | history:                        |

|    | math:                           |

|    | english:                        |

|    | chinese:                        |

|    | history:                        |

|    | biology:                        |

|    | history:                        |

|    | biology:                       |

+-----+-----------------------------------+

 rows in set (0.00 sec)

mysql>

mysql> SELECT a.sid,CONCAT(b.course_name,':',a.score)FROM score a INNER JOIN course b ON a.course_id=b.id;

23>.将所有老师的名字拆分成姓和名两个字段显示

mysql> SELECT name, SUBSTRING(name,,LOCATE(' ',name)- ),SUBSTRING(name,LOCATE(' ',name)+,) FROM teacher;

+-----------+---------------------------------------+---------------------------------------+

| name      | SUBSTRING(name,,LOCATE(' ',name)- ) | SUBSTRING(name,LOCATE(' ',name)+,) |

+-----------+---------------------------------------+---------------------------------------+

| Zhang san | Zhang                                 | san                                   |

| Li si     | Li                                    | si                                    |

| Wang wu   | Wang                                  | wu                                    |

| Liu liu   | Liu                                   | liu                                   |

| Ding qi   | Ding                                  | qi                                    |

+-----------+---------------------------------------+---------------------------------------+

 rows in set (0.00 sec)

mysql>

mysql>

mysql>

mysql> SELECT name, SUBSTRING(name,1,LOCATE(' ',name)- 1),SUBSTRING(name,LOCATE(' ',name)+1,50) FROM teacher;

24>.把所有学生的生日格式转换成年月日的格式，并计算每个学生年龄

mysql> SELECT sname,brithday,DATE_FORMAT(brithday, '%Y%m%d'),YEAR(NOW())- YEAR(brithday),FLOOR(DATEDIFF(NOW(),brithday)/) FROM students;

+-----------+---------------------+---------------------------------+-----------------------------+-------------------------------------+

| sname     | brithday            | DATE_FORMAT(brithday, '%Y%m%d') | YEAR(NOW())- YEAR(brithday) | FLOOR(DATEDIFF(NOW(),brithday)/) |

+-----------+---------------------+---------------------------------+-----------------------------+-------------------------------------+

| Jason Yin | -- :: |                         |                           |                                   |

| Andy      | -- :: |                         |                           |                                   |

| Bob       | -- :: |                         |                           |                                   |

| Ruth      | -- :: |                         |                           |                                   |

| Mike      | -- :: |                         |                           |                                   |

| John      | -- :: |                         |                           |                                   |

| Cindy     | -- :: |                         |                           |                                   |

| Susan     | -- :: |                         |                           |                                   |

+-----------+---------------------+---------------------------------+-----------------------------+-------------------------------------+

 rows in set (0.00 sec)

mysql>

mysql>

mysql>

mysql> SELECT sname,brithday,DATE_FORMAT(brithday, '%Y%m%d'),YEAR(NOW())- YEAR(brithday),FLOOR(DATEDIFF(NOW(),brithday)/365) FROM students;

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