mySQL练习题

练习1:

创建表以及数据已经给出,按照下列要求进行查询.

表:student

CREATE TABLE student(
    id INT,
    NAME VARCHAR(20),
    chinese FLOAT,
    english FLOAT,
    math FLOAT
);

INSERT INTO student(id,NAME,chinese,english,math) VALUES(1,'张小明',89,78,90);
INSERT INTO student(id,NAME,chinese,english,math) VALUES(2,'李进',67,53,95);
INSERT INTO student(id,NAME,chinese,english,math) VALUES(3,'王五',87,78,77);
INSERT INTO student(id,NAME,chinese,english,math) VALUES(4,'李一',88,98,92);
INSERT INTO student(id,NAME,chinese,english,math) VALUES(5,'李来财',82,84,67);
INSERT INTO student(id,NAME,chinese,english,math) VALUES(6,'张进宝',55,85,45);
INSERT INTO student(id,NAME,chinese,english,math) VALUES(7,'黄蓉',75,65,30);

-- 查询表中所有学生的信息。
select * from student 

-- 查询表中所有学生的姓名和对应的英语成绩。;
select name ,english from student

-- 统计每个学生的总分。
select chinese+english+math 总份额 from student;

-- 在所有学生总分数上加10分特长分。
select chinese+english+math+10 总份额 from student;

-- 使用别名表示学生分数。
select chinese 中文,english 英语,math 数学 from student;

-- 查询姓名为李一的学生成绩
select chinese,english,math from student where name ='李一'

-- 查询英语成绩大于90分的同学
select NAME from student where english>90                                         

-- 查询总分大于200分的所有同学
select NAME from student where (chinese+english+math)>200;

-- 查询英语分数在 80－90之间的同学
SELECT NAME from student where english between 80 and 90;

练习2:

部门表/员工表/工资登记表 以及数据已经给出,按照要求查询.

表emp:

表salgrade:

表dept:

-- 部门表
CREATE TABLE DEPT(
    DEPTNO INT PRIMARY KEY,
    DNAME VARCHAR(14), -- 部门名称
    LOC VARCHAR(13)-- 部门地址
) ;        
INSERT INTO DEPT VALUES    (10,'ACCOUNTING','NEW YORK');
INSERT INTO DEPT VALUES (20,'RESEARCH','DALLAS');
INSERT INTO DEPT VALUES    (30,'SALES','CHICAGO');
INSERT INTO DEPT VALUES    (40,'OPERATIONS','BOSTON');
    

-- 员工表
DROP TABLE EMP;
CREATE TABLE EMP(
    EMPNO INT  PRIMARY KEY, -- 员工编号
    ENAME VARCHAR(10), -- 员工姓名
    JOB VARCHAR(9), -- 员工工作
    MGR INT, -- 员工直属领导编号
    HIREDATE DATE, -- 入职时间
    SAL DOUBLE, -- 工资
    COMM DOUBLE, -- 奖金
    DEPTNO INT,  -- 所在部门
    FOREIGN KEY (DEPTNO) REFERENCES DEPT(DEPTNO));  -- 关联dept表    
    
-- ALTER TABLE EMP ADD FOREIGN KEY (DEPTNO) REFERENCES DEPT(DEPTNO);
INSERT INTO EMP VALUES(7369,'SMITH','职员',7566,"1980-12-17",800,NULL,20);
INSERT INTO EMP VALUES(7499,'ALLEN','销售员',7698,'1981-02-20',1600,300,30);
INSERT INTO EMP VALUES(7521,'WARD','销售员',7698,'1981-02-22',1250,500,30);
INSERT INTO EMP VALUES(7566,'JONES','经理',7839,'1981-04-02',2975,NULL,20);
INSERT INTO EMP VALUES(7654,'MARTIN','销售员',7698,'1981-09-28',1250,1400,30);
INSERT INTO EMP VALUES(7698,'BLAKE','经理',7839,'1981-05-01',2850,NULL,30);
INSERT INTO EMP VALUES(7782,'CLARK','经理',7839,'1981-06-09',2450,NULL,10);
INSERT INTO EMP VALUES(7788,'SCOTT','职员',7566,'1987-07-03',3000,2000,20);
INSERT INTO EMP VALUES(7839,'KING','董事长',NULL,'1981-11-17',5000,NULL,10);
INSERT INTO EMP VALUES(7844,'TURNERS','销售员',7698,'1981-09-08',1500,50,30);
INSERT INTO EMP VALUES(7876,'ADAMS','职员',7566,'1987-07-13',1100,NULL,20);
INSERT INTO EMP VALUES(7900,'JAMES','职员',7698,'1981-12-03',1250,NULL,30);
INSERT INTO EMP VALUES(7902,'FORD','销售员',7566,'1981-12-03',3000,NULL,20);
INSERT INTO EMP VALUES(7934,'MILLER','职员',7782,'1981-01-23',1300,NULL,10);

-- 工资等级表
CREATE TABLE SALGRADE( 
    GRADE INT,-- 等级
    LOSAL DOUBLE, -- 最低工资
    HISAL DOUBLE ); -- 最高工资

INSERT INTO SALGRADE VALUES (1,500,1000);
INSERT INTO SALGRADE VALUES (2,1001,1500);
INSERT INTO SALGRADE VALUES (3,1501,2000);
INSERT INTO SALGRADE VALUES (4,2001,3000);
INSERT INTO SALGRADE VALUES (5,3001,9999);

-- 1、查找部门30中员工的详细信息。
select * from EMP where DEPTNO=30;

-- 2、找出从事职员工作的员工的编号、姓名、部门号。
select EMPNO, ENAME ,DEPTNO from EMP where JOB ='职员'

-- 3、检索出奖金多于基本工资的员工信息。
select * from EMP where COMM>SAL

-- 4、检索出奖金多于基本工资60%的员工信息。
select * from EMP where comm>(0.6*SAL)

-- 5、找出姓名中包含A的员工信息。
select * from EMP where ENAME like '%A%'

-- 6、找出姓名以A、B、S开始的员工信息。

select * from EMP where ENAME like 'A%' || ENAME like 'B%' || ENAME like'S%'
-- 7、找到名字长度为7个字符的员工信息。
select * from EMP where ENAME like '_______'

-- 8、名字中不包e符的员工信息。


select * from EMP where ENAME not in (
    select ENAME from EMP where ENAME like '%R%'
);

select * from EMP where ENAME not like '%R%'

select * from EMP where !( ENAME like '%R%')

-- 9、返回员工的详细信息并按姓名升序排序。
select * from EMP ORDER BY ENAME

-- 10、返回员工的信息并按姓名降序,工资升序排列。
select * from EMP ORDER BY ENAME DESC ,SAL ASC

-- 11、计算员工的日薪(按30天)。
SELECT ENAME,ROUND(SAL/30, 2) from EMP

-- 12、找出获得奖金的员工的工作。
select JOB from EMP where COMM>0;

-- 13、找出奖金少于100或者没有获得奖金的员工的信息。
select * from EMP where COMM<100 ||  ISNULL(COMM)

-- 14、找出10部门的经理、20部门的职员 的员工信息。
select *from EMP where (JOB='经理' && DEPTNO=10) || (JOB='职员' && DEPTNO=20) 

-- 15、找出10部门的经理、20部门的职员 或者既不是经理也不是职员但是工资高于2000元的员工信息。
select *from EMP where (JOB='经理' && DEPTNO=10) 
|| (JOB='职员' && DEPTNO=20) 
|| (JOB!='经理' && JOB!='职员' && SAL>2000)

 练习3:

创建employee表,表结构及内容已经给出:

表employee:

CREATE TABLE employee(
    id INT,
    NAME VARCHAR(20),
    sex VARCHAR(10),
    birthday DATE,
    salary FLOAT,    
    RESUME TEXT
);
INSERT INTO employee VALUES(1,"zhangsan","male","1980-11-25",2000,"good body");
INSERT INTO employee VALUES(2,"lisi","male","1980-04-25",1000,"good body");
INSERT INTO employee VALUES(3,"xiaohong","female","1978-11-25",4000,"good girl");

select* from employee;
-- 将所有员工薪水修改为5000元。
update employee set salary=5000;
-- 将姓名为’zhangsan’的员工薪水修改为3000元。
update employee set salary=3000 where name='zhangsan'
-- 将姓名为’lisi’的员工薪水修改为4000元,sex改为female。
update employee set salary=4000,sex='female' where name ='lisi';
-- 将xiaohong的薪水在原有基础上增加1000元。
update employee set salary = salary+1000 where name ='xiaohong';

练习4:

创建表employee_test,表结构 以及表数据已经给出:

表employee_test:

create table employee_test(
id   int(11) ,
name   varchar(20),
sex   varchar(10),
birthday   date ,
salary   float(10,2) ,  -- 薪水
bonus   float(10,2) ,   -- 奖金
department varchar(20), -- 部门
resume   varchar(200) -- 简介
);
 
 
-- 插入员工数据
insert  into  employee_test values
(1,'zhangsan','male','1980-11-25',2000,100,'总裁办','good body'),
(2,'lisi','male','1980-04-25',1000,200,'研发部','good body'),
(3,'xiaohong','female','1978-11-25',4000,100,'财务部','good girl'),
(4,'wangwu','male','1981-01-25',4000,400,'人事部','good body'),
(5,'zhaoliu','male','1978-12-25',2000,NULL,'人事部','good body'),
(6,'tianqi','female','1998-05-25',2000,100,'人事部','good girl'),
(7,'renba','male','1968-10-25',3000,500,'财务部','good body');
 
 1. 查询表中所有员工的信息。
select * from employee_test;
2. 查询表中所有员工的姓名和对应的薪水。
select name ,salary from employee_test ;
3. 使用汉语展示员工信息。(列名翻译成中文展示)
select id 编号,name 名字,sex 性别, birthday 生日,salary 薪水, bonus 奖金,department 部门, resume 备注 from employee_test;
4. 查询姓名为zhangsan的员工的薪水
select salary from employee_test where name='zhangsan';
5. 查询姓名为zhangsan的员工的总收入
select salary+bonus 总收入 from employee_test where name='zhangsan';
6. 查询薪水大于3000的员工信息
select * from employee_test where (salary+bonus)>3000;
7. 查询总收入大于4000的员工的姓名 部门 薪水 奖金
select name,department,salary,bonus from employee_test where (salary+bonus)>4000;
8. 查询80后的员工
select * from employee_test where birthday>'1980-1-1';
9. 查询所有女性薪水大于4000的
select * from employee_test where salary>=4000 and sex='female';
10. 查询所有女性薪水大于4000的员工按薪水降序排列
select * from employee_test where salary>=4000 and sex='female' order by salary;
11. 查询各个部门员工数量
select department,COUNT(*) from employee_test group by department;
12. 查询各个部门的员工数量及薪水支出
select department,COUNT(*), salary from employee_test group by department;
13. 查询各个部门的员工数量及总支出
select department,COUNT(*), salary+bonus from employee_test group by department;
14. 查询公司男性和女性的数量
select sex,COUNT(*) from employee_test group by sex;
15. 查询公司男性员工和女性员工的收入总和
select sex,SUM(salary)+SUM(bonus) from employee_test group by sex;
16. 查询公司中男性员工的收入总和
select sex,SUM(salary)+SUM(bonus) from employee_test where sex='male';
17. 查询公司中总支出大于9000的部门
select department, salary+IFNULL(bonus,0) sumgongzi  from employee_test group by department HAVING sumgongzi>=9000;
18. 查询公司中所有zhang姓员工的平均工资
select AVG(salary) from employee_test where name like 'zhang%';
19. 查询公司中zhang姓员工的工资总和
select SUM(salary) from employee_test where name like 'zhang%';
20. 查询公司中zhang姓员工的总收入
select SUM(salary)+SUM(bonus) from employee_test where name like 'zhang%';

练习5:

从创建表stu,表的结构以及表的数据已经给出.

CREATE TABLE stu (
    id INT,-- 编号
    NAME VARCHAR ( 20 ),-- 姓名
    age INT,-- 年龄
    sex VARCHAR ( 5 ),-- 性别
    address VARCHAR ( 100 ),-- 地址
    math INT,-- 数学
    english INT -- 英语
    
);

INSERT INTO stu ( id, NAME, age, sex, address, math, english )
VALUES
    ( 1, '马云', 55, '男', '杭州', 66, 78 ),
    ( 2, '马化腾', 45, '女', '深圳', 98, 87 ),
    ( 3, '马景涛', 55, '男', '香港', 56, 77 ),
    ( 4, '柳岩', 20, '女', '湖南', 76, 65 ),
    ( 5, '柳青', 20, '男', '湖南', 86, NULL ),
    ( 6, '刘德华', 57, '男', '香港', 99, 99 ),
    ( 7, '马德', 22, '女', '香港', 99, 99 ),
    ( 8, '德玛西亚', 18, '男', '南京', 56, 65 );

-- 查询stu表中的所有数据
select * from stu;
-- 查询学生的姓名 及数学分数
select name ,math from stu;
-- 查询学生的姓名 及数学分数 总分 
select name ,math,SUM(math)+SUM(english);
-- 查询姓名叫马云
SELECT name from stu where name ='马云';
-- 查询英语成绩大于90分的学员
select * from stu where english>90;
-- 查询英语成绩大于60 分小于90分 
select * from stu where english between 60 and 90;
-- 查询英语成绩大于60 分小于90分  的学员的姓名和地址
select name ,address from stu where english between  60 and 90;
-- 查询姓名叫马云 或者姓名叫做马化腾或 柳青  的学员
select name from stu where name='马云' and name ='马化腾' and name='柳青';
-- 查询没有英语成绩的学员
select name from stu where ISNULL(english);
-- 查询有英语成绩的学员
select name from stu where english is not null;
-- 查询有英语成绩的学员 并且英语成绩 在60 - 80分之间
select name,english from stu where english between 60 and 80;
-- 查询有英语成绩的学员 并且英语成绩 在60 - 80分之间   并且来自于杭州

select name from stu where english between 60 and 80 and address='杭州';


-- 查询名称中包含青的学员
select name from stu where name='%青%';
-- 查询名称中以德结尾的学员
select name from stu where name='%德';
-- 查询姓马学员,并且名字只有二位字符
select name from stu where name='马%';
-- 查询学员信息,按照数学成绩升序排序  如果数学成绩相同按照英语成绩降序
select * from stu order by math,english DESC;
-- 查询学生信息,按照英语升序排序
select * from stu english;
-- 计算学生的个数
select count(*) from stu;
-- 计算所有学生的数学平均成绩
select avg(math) from stu;
-- 计算所有学生数学成绩的总和 和英语成绩的总和
select sum(math) , sum(english) from stu;
-- 计算所有学生数学成绩+英语成绩的总和
select sum(math)+sum(english) from stu;
-- 查询各个地区的学生的数量
select  address,COUNT(address) as 地区 from stu group by address;
-- 查询各个地区的数学分数在70分以上的学生的数量
select address,COUNT(address) from stu where math>70 group by address ;
-- 查询各个地区的数学分数在70分以上的学生的数量 并且 学生人数大于2人
select address,COUNT(address) as countnum from stu where math>70 group by address HAVING countnum>=2;
-- 获取学生数据  获取第二页 每页显示5条  (2-1)*5
select * from stu limit 1,5;

练习6

创建部门表,创建员工表,表结构以及数据已经给出.

部门表 :

员工表:

 

-- 创建部门表
CREATE TABLE dept(
 id INT PRIMARY KEY AUTO_INCREMENT,
 NAME VARCHAR(20)
);

INSERT INTO dept (NAME) VALUES ('开发部'),('市场部'),('财务部');


-- 创建员工表
CREATE TABLE emp (
 id INT PRIMARY KEY AUTO_INCREMENT,
 NAME VARCHAR(10),
 gender CHAR(1), -- 性别
 salary DOUBLE, -- 工资
 join_date DATE, -- 入职日期
 dept_id INT,
 FOREIGN KEY (dept_id) REFERENCES dept(id) -- 外键，关联部门表(部门表的主键)
);


INSERT INTO emp(NAME,gender,salary,join_date,dept_id) VALUES('孙悟空','男',7200,'2013-02-24',1);
INSERT INTO emp(NAME,gender,salary,join_date,dept_id) VALUES('猪八戒','男',3600,'2010-12-02',2);

INSERT INTO emp(NAME,gender,salary,join_date,dept_id) VALUES('唐僧','男',9000,'2008-08-08',2);
INSERT INTO emp(NAME,gender,salary,join_date,dept_id) VALUES('白骨精','女',5000,'2015-10-07',3);
INSERT INTO emp(NAME,gender,salary,join_date,dept_id) VALUES('蜘蛛精','女',4500,'2011-03-14',1);

--查询所有的员工信息 和对应的部门信息
select * from emp,dept where emp.`dept_id` = dept.`id`;

--查询员工表的名称,性别,部门表的名称
select 
            t1.name,
            t1.gender,
            t2.name
FROM
            emp t1,
            dept t2
WHERE 
            t1.`dept_id` = t2.`id`;
            

--内连接(取交集)
select emp.name,emp.gender,dept.name from emp inner join dept on emp.dept_id=dept.id


--添加一个新的职工 小明
insert into emp values(6,'小明','男',null,null,null) 

--左连接查询
select * from emp left outer join dept on emp.dept_id=dept.id

--右连接查询
select * from emp right outer join dept on emp.dept_id=dept.id

--添加一个新的部门
select * from dept
insert into dept values(4,'公关部')

--查询工资最高的员工信息
select
    *
from
    emp
where
    emp.salary>=(select MAX(salary) from emp);
    
--查询最高的工资是多少 9000
select MAX(salary) from emp;

--查询员工的信息,并且工资等于9000
select *from emp where emp.salary =9000;

--一条sql就完成这个操作.

select * from emp where emp.salary=(select MIN(salary) from emp);

--查询员工的工资小于平均工资的人  单行单列

select emp.`NAME` from emp where emp.salary <(select AVG(salary) from emp);

--查询财务部所有的员工信息
select * from emp where emp.dept_id in (select id from dept where dept.name='财务部');
 
--查询财务部所有的员工信息 和 市场部的员工信息  多行单列
select * from emp where emp.dept_id in (select id from dept where dept.name='财务部' or name='市场部');

select * from emp where emp.dept_id in(3,2);


--查询 员工的入职日期是2011-11-11 之后的员工信息 和 部门信息 .多行多列

select  emp.id,emp.`NAME`, dept.`NAME`,emp.gender,emp.salary,emp.join_date,emp.dept_id from emp,dept where  join_date>'2011-11-11' and emp.dept_id=dept.id;

select * from emp,dept where  join_date>'2011-11-11' and emp.dept_id=dept.id;


select * from dept t1, (select * from emp where emp.join_date > '2011-11-11') t2 where t1.id = t2.dept_id;

select * from emp t1, dept t2 where t1.dept_id =t2.id and t1.join_date >'2011-11-11';

--左外
select * from emp a left join dept b on a.dept_id = b.id where a.join_date>'2011-11-11';

练习7:

按照下列图示要求创建数据库表:

 

Create table user(
 uid int PRIMARY KEY,
 uname varchar(20) not NULL,
 pwd varchar(20),
 email varchar(20) UNIQUE

);

CREATE TABLE product(
    pid int PRIMARY KEY,
    pname varchar(20) not NULL,
    intro varchar(10),
    price double (10,2) not null
)

CREATE TABLE orders(
    oid int PRIMARY KEY,
    orderno varchar(20) not NULL,
    ordertime date,
    totalprice double (10,2) not null

)
CREATE TABLE order_detail(
    did int PRIMARY KEY,
    oid int not null,
    pid int not null,
    num int not null,
    price double (10,2) not null
)

CREATE TABLE category(
    cid int PRIMARY key,
    cname VARCHAR(20) not null

)

练习8:

题目给定表book/borrow/student 结构以及数据,按照要求进行查询:

表book:

 

表borrow:

表student:

 

CREATE TABLE  book (
  BID CHAR(10) NOT NULL,
  title CHAR(50) DEFAULT NULL,
  author CHAR(20) DEFAULT NULL,
  PRIMARY KEY (BID)
);
INSERT INTO book VALUES ('B001', '人生若只如初见', '安意如');
INSERT INTO book VALUES ('B002', '入学那天遇见你', '晴空');
INSERT INTO book VALUES ('B003', '感谢折磨你的人', '如娜');
INSERT INTO book VALUES ('B004', '我不是教你诈', '刘庸');
INSERT INTO book VALUES ('B005', '英语四级', '白雪');
CREATE TABLE  borrow (
  borrowID CHAR(10) NOT NULL,
  stuID CHAR(10) DEFAULT NULL,
  BID CHAR(10) DEFAULT NULL,
  T_time VARCHAR(50) DEFAULT NULL,
  B_time VARCHAR(50) DEFAULT NULL,
  PRIMARY KEY (borrowID)
) ;
INSERT INTO borrow VALUES ('T001', '1001', 'B001', '2007-12-26 00:00:00', NULL);
INSERT INTO borrow VALUES ('T002', '1004', 'B003', '2008-01-05 00:00:00', NULL);
INSERT INTO borrow VALUES ('T003', '1005', 'B001', '2007-10-08 00:00:00', '2007-12-25 00:00:00');
INSERT INTO borrow VALUES ('T004', '1005', 'B002', '2007-12-16 00:00:00', '2008-01-07 00:00:00');
INSERT INTO borrow VALUES ('T005', '1002', 'B004', '2007-12-22 00:00:00', NULL);
INSERT INTO borrow VALUES ('T006', '1005', 'B005', '2008-01-06 00:00:00', NULL);
INSERT INTO borrow VALUES ('T007', '1002', 'B001', '2007-09-11 00:00:00', NULL);
INSERT INTO borrow VALUES ('T008', '1005', 'B004', '2007-12-10 00:00:00', NULL);
INSERT INTO borrow VALUES ('T009', '1004', 'B005', '2007-10-16 00:00:00', '2007-12-18 00:00:00');
INSERT INTO borrow VALUES ('T010', '1002', 'B002', '2007-09-15 00:00:00', '2008-01-05 00:00:00');
INSERT INTO borrow VALUES ('T011', '1004', 'B003', '2007-12-28 00:00:00', NULL);
INSERT INTO borrow VALUES ('T012', '1002', 'B003', '2007-12-30 00:00:00', NULL);

CREATE TABLE  student (
  stuID CHAR(10) NOT NULL,
  stuName VARCHAR(10) DEFAULT NULL,
  major VARCHAR(50) DEFAULT NULL,
  PRIMARY KEY (stuID)
);

INSERT INTO student VALUES ('1001', '林林', '计算机');
INSERT INTO student VALUES ('1002', '白杨', '计算机');
INSERT INTO student VALUES ('1003', '虎子', '英语');
INSERT INTO student VALUES ('1004', '北漂的雪', '工商管理');
INSERT INTO student VALUES ('1005', '五月', '数学');

/*
1.    查询“计算机”专业学生在“2007-12-15”至“2008-1-8”时间段内借书的学生编号、学生名称、图书编号、图书名称、借出日期；
2.    查询所有借过图书的学生编号、学生名称、专业；
3.    查询没有借过图书的学生编号、学生名称、专业；
4.    查询借过作者为“安意如”的图书的学生姓名、图书名称、借出日期、归还日期；
5.    查询借过书但有书未归还的学生编号、学生名称、图书编号、图书名称、借出日期
6.    查询目前借书但未归还图书的学生名称及未还图书数量；
*/
--查询“计算机”专业学生在“2007-12-15”至“2008-1-8”时间段内借书的学生编号、学生名称、图书编号、图书名称、借出日期；
select
    t1.stuID,
    t1.stuName,
    t3.BID,
    t3.title,
    t2.T_time
from
    student t1,
    borrow t2,
    book t3
where
    t1.stuID=t2.stuID and
    t3.BID=t2.BID and
    t1.major='计算机' and
    t2.T_time between '2007-12-15' and '2008-1-8';
--查询所有借过图书的学生编号、学生名称、专业；
select 
    DISTINCT
    t2.stuID,
    t2.stuName,
    t2.major
from
    borrow t1,
    student t2
where
    t1.stuID=t2.stuID
    --3.    查询没有借过图书的学生编号、学生名称、专业；

select
    student.stuID,
    student.stuName,
    student.major
from
    student
where student.stuID not in(
select
    t1.stuID
from
    borrow t1,
    student t2
where
 t1.stuID=t2.stuID
);

select
    t1.stuID
from
    borrow t1,
    student t2
where
 t1.stuID=t2.stuID;
--4.    查询借过作者为“安意如”的图书的学生姓名、图书名称、借出日期、归还日期；
select 
    student.stuName,
    book.title,
    borrow.T_time,
    borrow.B_time
from 
    student,borrow,book
where 
    student.stuID=borrow.stuID and
    book.BID=borrow.BID and
    book.author='安意如';

--5.    查询借过书但有书未归还的学生编号、学生名称、图书编号、图书名称、借出日期
select
    t1.stuID,
    t1.stuName,
    t3.BID,
    t3.title,
    t2.T_time
    
from
    student t1,
    borrow t2,
    book t3
where
    t1.stuID=t2.stuID and
    t3.BID=t2.BID and
    ISNULL(t2.B_time);

--6.    查询目前借书但未归还图书的学生名称及未还图书数量；
select
    
    t1.stuID,
    t1.stuName,
    count(t2.BID)
from
    student t1,
    borrow t2,
    book t3
where
    t1.stuID=t2.stuID and
    t3.BID=t2.BID and
    ISNULL(t2.B_time)
    GROUP BY t2.stuID;