1、查询有任课教师的姓名和department:
课程表：
mysql> select * from course; +----------+-----------+---------+ | cour_num | cour_name | tea_num | +----------+-----------+---------+ | 1-245 | Math | 0438 | | 2-271 | Circuit | 0435 | | 3-105 | OS | 0435 | | 4-321 | Bio | 0436 | +----------+-----------+---------+
教师表：
mysql> select * from teacher; +---------+-------------+---------+---------------------+----------+------------+ | tea_num | tea_name | tea_sex | tea_birth | tea_prof | department | +---------+-------------+---------+---------------------+----------+------------+ | 0435 | LiMei | F | 1983-02-24 00:00:00 | prof | Computer | | 0436 | MaDi | F | 1984-01-23 00:00:00 | assist | Bio | | 0437 | LiZhe | F | 1974-01-23 00:00:00 | prof | Econ | | 0438 | ShaoGuoYing | F | 1985-06-17 00:00:00 | prof | Math | | 0439 | Susan | F | 1985-07-18 00:00:00 | assist | Math | | 0440 | Mary | F | 1990-05-02 00:00:00 | lecturer | Econ | +---------+-------------+---------+---------------------+----------+------------+
我的：
mysql> select cour_num,tea_name,department from course,teacher -> where course.tea_num=teacher.tea_num; +----------+-------------+------------+ | cour_num | tea_name | department | +----------+-------------+------------+ | 2-271 | LiMei | Computer | | 3-105 | LiMei | Computer | | 4-321 | MaDi | Bio | | 1-245 | ShaoGuoYing | Math | +----------+-------------+------------+
实际的：
mysql> select tea_name,department from teacher -> where tea_num in (select tea_num from course); +-------------+------------+ | tea_name | department | +-------------+------------+ | LiMei | Computer | | MaDi | Bio | | ShaoGuoYing | Math | +-------------+------------+
2、查询至少有2名男生的班号：（条件加分组查询）
学生表：
mysql> select * from student; +---------+----------+---------+---------------------+-------+ | stu_num | stu_name | stu_sex | stu_birth | class | +---------+----------+---------+---------------------+-------+ | 11215 | JiaWei | F | 1993-07-28 00:00:00 | 112 | | 11328 | DingQi | F | 1994-08-15 00:00:00 | 113 | | 11422 | Baker | F | 1999-09-22 00:00:00 | 114 | | 11423 | Bob | M | 1998-04-25 00:00:00 | 114 | | 11424 | LinJie | M | 1994-06-12 00:00:00 | 114 | | 11425 | XieZhou | M | 1995-03-11 00:00:00 | 114 | | 11426 | MingHui | F | 1998-08-09 00:00:00 | 114 | | 11427 | NanNan | F | 1995-10-20 00:00:00 | 114 | +---------+----------+---------+---------------------+-------+
实际操作：
mysql> select class from student -> where stu_sex='M' group by class having count(*)>=2; +-------+ | class | +-------+ | 114 | +-------+
3、查询student表中姓名不以B开头的同学记录：
mysql> select * from student -> where stu_name not like 'B%'; +---------+----------+---------+---------------------+-------+ | stu_num | stu_name | stu_sex | stu_birth | class | +---------+----------+---------+---------------------+-------+ | 11215 | JiaWei | F | 1993-07-28 00:00:00 | 112 | | 11328 | DingQi | F | 1994-08-15 00:00:00 | 113 | | 11424 | LinJie | M | 1994-06-12 00:00:00 | 114 | | 11425 | XieZhou | M | 1995-03-11 00:00:00 | 114 | | 11426 | MingHui | F | 1998-08-09 00:00:00 | 114 | | 11427 | NanNan | F | 1995-10-20 00:00:00 | 114 | +---------+----------+---------+---------------------+-------+
4、查询student表中每个学生的姓名和年龄：
当前年份：year函数与now函数：
mysql> select year(now()); +-------------+ | year(now()) | +-------------+ | 2020 | +-------------+
学生出生年份：
mysql> select stu_name,year(stu_birth) from student; +----------+-----------------+ | stu_name | year(stu_birth) | +----------+-----------------+ | JiaWei | 1993 | | DingQi | 1994 | | Baker | 1999 | | Bob | 1998 | | LinJie | 1994 | | XieZhou | 1995 | | MingHui | 1998 | | NanNan | 1995 | +----------+-----------------+
别忘了取个别名：
mysql> select stu_name,year(now())-year(stu_birth) as age from student; +----------+------+ | stu_name | age | +----------+------+ | JiaWei | 27 | | DingQi | 26 | | Baker | 21 | | Bob | 22 | | LinJie | 26 | | XieZhou | 25 | | MingHui | 22 | | NanNan | 25 | +----------+------+
5、查询student表中最大和最小的birthday日期值：max()与min()
mysql> select max(stu_birth),min(stu_birth) from student; +---------------------+---------------------+ | max(stu_birth) | min(stu_birth) | +---------------------+---------------------+ | 1999-09-22 00:00:00 | 1993-07-28 00:00:00 | +---------------------+---------------------+
实际上，max的年份数字大于min的年份数字，但是应该年份越大的年龄越小才对。
mysql> select max(stu_birth) as '最小',min(stu_birth) as '最大' from student; +---------------------+---------------------+ | 最小 | 最大 | +---------------------+---------------------+ | 1999-09-22 00:00:00 | 1993-07-28 00:00:00 | +---------------------+---------------------+
6、以班号和年龄从大到小的顺序查询student表中的全部记录：
mysql> select * from student order by class desc,stu_birth asc; +---------+----------+---------+---------------------+-------+ | stu_num | stu_name | stu_sex | stu_birth | class | +---------+----------+---------+---------------------+-------+ | 11424 | LinJie | M | 1994-06-12 00:00:00 | 114 | | 11425 | XieZhou | M | 1995-03-11 00:00:00 | 114 | | 11427 | NanNan | F | 1995-10-20 00:00:00 | 114 | | 11423 | Bob | M | 1998-04-25 00:00:00 | 114 | | 11426 | MingHui | F | 1998-08-09 00:00:00 | 114 | | 11422 | Baker | F | 1999-09-22 00:00:00 | 114 | | 11328 | DingQi | F | 1994-08-15 00:00:00 | 113 | | 11215 | JiaWei | F | 1993-07-28 00:00:00 | 112 | +---------+----------+---------+---------------------+-------+
先按照班级排序，再按照年龄排序的。
7、查询最高分同学stu_num、cour_num、degree：
mysql> select * from score -> where degree=(select max(degree) from score); +---------+----------+--------+ | stu_num | cour_num | degree | +---------+----------+--------+ | 11422 | 3-105 | 92 | +---------+----------+--------+
8、查询与Bob同学同性别的所有同学的名字：
mysql> select stu_name from student -> where stu_sex=(select stu_sex from student where stu_name='Bob'); +----------+ | stu_name | +----------+ | Bob | | LinJie | | XieZhou | +----------+
和Bob同班同性别的同学的姓名：
mysql> select stu_name from student -> where stu_sex=(select stu_sex from student where stu_name='Bob') -> and class=(select class from student where stu_name='Bob'); +----------+ | stu_name | +----------+ | Bob | | LinJie | | XieZhou | +----------+
9、查询选修数学课程的女同学的成绩表：
女同学学号：
mysql> select stu_num from student -> where stu_sex='F'; +---------+ | stu_num | +---------+ | 11215 | | 11328 | | 11422 | | 11426 | | 11427 | +---------+
数学编号：
mysql> select cour_num from course -> where cour_name='Math'; +----------+ | cour_num | +----------+ | 1-245 | +----------+
成绩表：
mysql> select * from score; +---------+----------+--------+ | stu_num | cour_num | degree | +---------+----------+--------+ | 11422 | 3-105 | 92 | | 11423 | 1-245 | 84 | | 11423 | 2-271 | 75 | | 11424 | 4-321 | 75 | | 11425 | 2-271 | 89 | | 11426 | 1-245 | 61 | | 11426 | 2-271 | 82 | | 11427 | 1-245 | 78 | +---------+----------+--------+
筛选：
mysql> select * from score -> where stu_num in (select stu_num from student where stu_sex='F') -> and cour_num=(select cour_num from course where cour_name='Math'); +---------+----------+--------+ | stu_num | cour_num | degree | +---------+----------+--------+ | 11426 | 1-245 | 61 | | 11427 | 1-245 | 78 | +---------+----------+--------+
10、查询所有同学的stu_num、cour_num、rank列：
创建一个等级表：
mysql> create table grade( -> low int(3), -> high int(3), -> grade char(1) -> );
插入数据后的grade表：
mysql> SELECT * FROM grade; +------+------+-------+ | low | high | grade | +------+------+-------+ | 90 | 100 | A | | 80 | 89 | B | | 70 | 79 | C | | 60 | 69 | D | | 0 | 59 | E | +------+------+-------+
成绩表：
mysql> select * from score; +---------+----------+--------+ | stu_num | cour_num | degree | +---------+----------+--------+ | 11422 | 3-105 | 92 | | 11423 | 1-245 | 84 | | 11423 | 2-271 | 75 | | 11424 | 4-321 | 75 | | 11425 | 2-271 | 89 | | 11426 | 1-245 | 61 | | 11426 | 2-271 | 82 | | 11427 | 1-245 | 78 | +---------+----------+--------+
结果：
mysql> select stu_num,cour_num,grade from score,grade -> where degree between low and high; +---------+----------+-------+ | stu_num | cour_num | grade | +---------+----------+-------+ | 11422 | 3-105 | A | | 11423 | 1-245 | B | | 11423 | 2-271 | C | | 11424 | 4-321 | C | | 11425 | 2-271 | B | | 11426 | 1-245 | D | | 11426 | 2-271 | B | | 11427 | 1-245 | C | +---------+----------+-------+