作业

作业

创建表

##创建class表
mysql> show create table class ;
| Table | Create Table                                                               
+-------+------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| class | CREATE TABLE `class` (
  `cid` int(11) NOT NULL AUTO_INCREMENT,
  `caption` varchar(30) DEFAULT NULL,
  PRIMARY KEY (`cid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+-------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------
mysql>

##创建course 表
mysql> show create table course;  

| course | CREATE TABLE `course` (
  `cid` int(11) NOT NULL AUTO_INCREMENT,
  `cname` varchar(10) NOT NULL DEFAULT '',
  `tearch_id` int(11) NOT NULL,
  PRIMARY KEY (`cid`),
  KEY `teacher_id` (`tearch_id`),
  CONSTRAINT `teacher_id` FOREIGN KEY (`tearch_id`) REFERENCES `teacher` (`tid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+--------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.01 sec)

## 创建score 表
| Table | Create Table                                                                
| score | CREATE TABLE `score` (
  `sid` int(11) NOT NULL AUTO_INCREMENT,
  `student_id` int(11) NOT NULL,
  `corse_id` int(11) NOT NULL,
  `number` int(11) NOT NULL,
  PRIMARY KEY (`sid`),
  KEY `student1_id` (`student_id`),
  KEY `corse1_id` (`corse_id`),
  CONSTRAINT `corse1_id` FOREIGN KEY (`corse_id`) REFERENCES `course` (`cid`),
  CONSTRAINT `student1_id` FOREIGN KEY (`student_id`) REFERENCES `student` (`sid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |

## 创建student表
| Table   | Create Table                                                             
| student | CREATE TABLE `student` (
  `sid` int(11) NOT NULL AUTO_INCREMENT,
  `sname` varchar(30) DEFAULT NULL,
  `gender` enum('男','女') DEFAULT NULL,
  `class_id` int(11) NOT NULL DEFAULT '1',
  PRIMARY KEY (`sid`),
  KEY `student_class` (`class_id`),
  CONSTRAINT `student_class` FOREIGN KEY (`class_id`) REFERENCES `class` (`cid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+---------+--------------------------------------------------------------------------
1 row in set (0.00 sec)

## 创建teacher表
mysql> show create table teacher;
| Table   | Create Table                                                             
| teacher | CREATE TABLE `teacher` (
  `tid` int(11) NOT NULL AUTO_INCREMENT,
  `tname` varchar(30) NOT NULL DEFAULT '',
  PRIMARY KEY (`tid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+---------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.01 sec)

1. 查询所有大于60分的学生的姓名和学号 (DISTINCT: 去重)

mysql> select distinct * from score left join student on  student_id =  student.sid where number > 60 ;
+-----+------------+----------+--------+------+-------+--------+----------+
| sid | student_id | corse_id | number | sid  | sname | gender | class_id |
+-----+------------+----------+--------+------+-------+--------+----------+
|  10 |         11 |        8 |    100 |   11 | 山    | 男     |        2 |
+-----+------------+----------+--------+------+-------+--------+----------+
1 row in set (0.00 sec)

mysql>

-- 2.查询每个老师教授的课程数量 和 老师信息

mysql> select tname,count(cname) from course left join teacher on tearch_id = teacher.tid group by tname ;
+-------+--------------+
| tname | count(cname) |
+-------+--------------+
| 波多  |            2 |
| 苍空  |            3 |
+-------+--------------+
2 rows in set (0.00 sec)

mysql> select * from teacher;
+-----+-------+
| tid | tname |
+-----+-------+
|   1 | 波多  |
|   2 | 苍空  |
|   3 | 饭岛  |
+-----+-------+
3 rows in set (0.00 sec)

mysql> select sid,sname,gender,caption from student left join class on class_id=class.cid;
+-----+-------+--------+------------+
| sid | sname | gender | caption    |
+-----+-------+--------+------------+
|   7 | 钢蛋  | 女     | 三年级二班 |
|   9 | 铁锤  | 男     | 三年级二班 |
|  10 | 山炮  | 女     | 三年级二班 |
|   8 | 钢蛋  | 女     | 一年级三班 |
|  11 | 山    | 男     | 一年级三班 |
+-----+-------+--------+------------+
5 rows in set (0.00 sec)