1170 lines
36 KiB
Markdown
1170 lines
36 KiB
Markdown
# 查询练习
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建表，插入数据
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新建一个查询用的数据库:selectTest
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CREATE DATABASE selectTest;
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选择该数据库:
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USE selectTest;
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学生表:
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student
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学号
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姓名
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性别
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出生日期
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所在班级
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```sql
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CREATE TABLE student(
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s_no VARCHAR(20) PRIMARY KEY COMMENT'学生学号',
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s_name VARCHAR(20) NOT NULL COMMENT'学生姓名 不能为空',
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s_sex VARCHAR(10) NOT NULL COMMENT'学生性别',
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s_birthday DATETIME COMMENT'学生生日',
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s_class VARCHAR(20) COMMENT'学生所在的班级'
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)ENGINE=InnoDB CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;
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```
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教师表
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teacher
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教师编号
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教师名字
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教师性别
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出生日期
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职称
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所在部门
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```sql
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CREATE TABLE teacher(
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t_no VARCHAR(20) PRIMARY KEY COMMENT'教师编号',
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t_name VARCHAR(20) NOT NULL COMMENT'教师姓名',
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t_sex VARCHAR(20) NOT NULL COMMENT'教师性别',
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t_birthday DATETIME COMMENT'教师生日',
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t_rof VARCHAR(20) NOT NULL COMMENT'教师职称',
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t_depart VARCHAR(20) NOT NULL COMMENT'教师所在的部门'
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)ENGINE=InnoDB CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;
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```
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课程表:
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course
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课程号
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课程课程名称
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教师编号
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```sql
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CREATE TABLE course(
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c_no VARCHAR(20) PRIMARY KEY COMMENT'课程号',
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c_name VARCHAR(20) NOT NULL COMMENT'课程名称',
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t_no VARCHAR(20) NOT NULL COMMENT'教师编号 外键关联teacher表',
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FOREIGN KEY(t_no) references teacher(t_no)
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)ENGINE=InnoDB CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;
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```
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成绩表
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srore
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学号
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课程号
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成绩
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注意:视频中原先只有一个主键s_no ,后来修改了
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```sql
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CREATE TABLE score (
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s_no VARCHAR(20) NOT NULL COMMENT'成绩表的编号 依赖学生学号',
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c_no VARCHAR(20) NOT NULL COMMENT'课程号 依赖于课程表中的c_id',
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sc_degree decimal,
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foreign key(s_no) references student(s_no),
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foreign key(c_no) references course(c_no),
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PRIMARY KEY(s_no,c_no)
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)ENGINE=InnoDB CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;
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```
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查看创建的表以及架构
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```sql
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SHOW TABLES;
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+----------------------+
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| Tables_in_selecttest |
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+----------------------+
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| course |
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| score |
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| student |
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| teacher |
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+----------------------+
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```
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查看student表结构 DESCRIBE student;
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```sql
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+------------+-------------+------+-----+---------+-------+
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| Field | Type | Null | Key | Default | Extra |
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+------------+-------------+------+-----+---------+-------+
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| s_no | varchar(20) | NO | PRI | NULL | |
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| s_name | varchar(20) | NO | | NULL | |
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| s_sex | varchar(10) | NO | | NULL | |
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| s_birthday | datetime | YES | | NULL | |
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| s_class | varchar(20) | YES | | NULL | |
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+------------+-------------+------+-----+---------+-------+
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```
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查看teacher表结构
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```sql
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DESCRIBE teacher;
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+------------+-------------+------+-----+---------+-------+
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| Field | Type | Null | Key | Default | Extra |
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+------------+-------------+------+-----+---------+-------+
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| t_no | varchar(20) | NO | PRI | NULL | |
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| t_name | varchar(20) | NO | | NULL | |
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| t_sex | varchar(20) | NO | | NULL | |
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| t_birthday | datetime | YES | | NULL | |
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| t_rof | varchar(20) | NO | | NULL | |
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| t_depart | varchar(20) | NO | | NULL | |
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+------------+-------------+------+-----+---------+-------+
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```
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查看course表结构
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```sql
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DESCRIBE course;
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+--------+-------------+------+-----+---------+-------+
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| Field | Type | Null | Key | Default | Extra |
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+--------+-------------+------+-----+---------+-------+
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| c_no | varchar(20) | NO | PRI | NULL | |
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| c_name | varchar(20) | NO | | NULL | |
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| t_no | varchar(20) | NO | MUL | NULL | |
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+--------+-------------+------+-----+---------+-------+
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```
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查看score表结构
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```sql
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DESCRIBE score;
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+-----------+---------------+------+-----+---------+-------+
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| Field | Type | Null | Key | Default | Extra |
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+-----------+---------------+------+-----+---------+-------+
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| s_no | varchar(20) | NO | PRI | NULL | |
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| c_no | varchar(20) | NO | MUL | NULL | |
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| sc_degree | decimal(10,0) | YES | | NULL | |
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+-----------+---------------+------+-----+---------+-------+
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```
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向表中添加数据
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```sql
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--学生表数据
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INSERT INTO student VALUES('101','曾华','男','1977-09-01','95033');
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INSERT INTO student VALUES('102','匡明','男','1975-10-02','95031');
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INSERT INTO student VALUES('103','王丽','女','1976-01-23','95033');
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INSERT INTO student VALUES('104','李军','男','1976-02-20','95033');
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INSERT INTO student VALUES('105','王芳','女','1975-02-10','95031');
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INSERT INTO student VALUES('106','陆军','男','1974-06-03','95031');
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INSERT INTO student VALUES('107','王尼玛','男','1976-02-20','95033');
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INSERT INTO student VALUES('108','张全蛋','男','1975-02-10','95031');
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INSERT INTO student VALUES('109','赵铁柱','男','1974-06-03','95031');
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--教师表数据
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INSERT INTO teacher VALUES('804','李诚','男','1958-12-02','副教授','计算机系');
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INSERT INTO teacher VALUES('856','张旭','男','1969-03-12','讲师','电子工程系');
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INSERT INTO teacher VALUES('825','王萍','女','1972-05-05','助教','计算机系');
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INSERT INTO teacher VALUES('831','刘冰','女','1977-08-14','助教','电子工程系');
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--添加课程表
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INSERT INTO course VALUES('3-105','计算机导论','825');
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INSERT INTO course VALUES('3-245','操作系统','804');
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INSERT INTO course VALUES('6-166','数字电路','856');
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INSERT INTO course VALUES('9-888','高等数学','831');
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--添加成绩表
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INSERT INTO score VALUES('103','3-245','86');
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INSERT INTO score VALUES('105','3-245','75');
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INSERT INTO score VALUES('109','3-245','68');
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INSERT INTO score VALUES('103','3-105','92');
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INSERT INTO score VALUES('105','3-105','88');
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INSERT INTO score VALUES('109','3-105','76');
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INSERT INTO score VALUES('103','6-166','85');
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INSERT INTO score VALUES('105','6-166','79');
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INSERT INTO score VALUES('109','6-166','81');
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```
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几张表的数据展现
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```sql
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SELECT * FROM student;
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+------+--------+-------+---------------------+---------+
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| s_no | s_name | s_sex | s_birthday | s_class |
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+------+--------+-------+---------------------+---------+
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| 101 | 曾华 | 男 | 1977-09-01 00:00:00 | 95033 |
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| 102 | 匡明 | 男 | 1975-10-02 00:00:00 | 95031 |
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| 103 | 王丽 | 女 | 1976-01-23 00:00:00 | 95033 |
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| 104 | 李军 | 男 | 1976-02-20 00:00:00 | 95033 |
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| 105 | 王芳 | 女 | 1975-02-10 00:00:00 | 95031 |
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| 106 | 陆军 | 男 | 1974-06-03 00:00:00 | 95031 |
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| 107 | 王尼玛 | 男 | 1976-02-20 00:00:00 | 95033 |
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| 108 | 张全蛋 | 男 | 1975-02-10 00:00:00 | 95031 |
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| 109 | 赵铁柱 | 男 | 1974-06-03 00:00:00 | 95031 |
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+------+--------+-------+---------------------+---------+
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teacher SELECT * FROM teacher;
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+------+--------+-------+---------------------+--------+------------+
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| t_no | t_name | t_sex | t_birthday | t_rof | t_depart |
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+------+--------+-------+---------------------+--------+------------+
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| 804 | 李诚 | 男 | 1958-12-02 00:00:00 | 副教授 | 计算机系 |
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| 825 | 王萍 | 女 | 1972-05-05 00:00:00 | 助教 | 计算机机系 |
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| 831 | 刘冰 | 女 | 1977-08-14 00:00:00 | 助教 | 电子工程系 |
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| 856 | 张旭 | 男 | 1969-03-12 00:00:00 | 讲师 | 电子工程系 |
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+------+--------+-------+---------------------+--------+------------+
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score SELECT * FROM score;
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+------+-------+-----------+
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| s_no | c_no | sc_degree |
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+------+-------+-----------+
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| 103 | 3-105 | 92 |
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| 103 | 3-245 | 86 |
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| 103 | 6-166 | 85 |
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| 105 | 3-105 | 88 |
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| 105 | 3-245 | 75 |
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| 105 | 6-166 | 79 |
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| 109 | 3-105 | 76 |
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| 109 | 3-245 | 68 |
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| 109 | 6-166 | 81 |
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+------+-------+-----------+
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course SELECT * FROM course;
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+-------+------------+------+
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| c_no | c_name | t_no |
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+-------+------------+------+
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| 3-105 | 计算机导论 | 825 |
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| 3-245 | 操作系统 | 804 |
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| 6-166 | 数字电路 | 856 |
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| 9-888 | 高等数学 | 831 |
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+-------+------------+------+
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```
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```sql
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select * from student;
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select s_name,s_sex,s_class from student;
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1.筛选出老师属于哪些专业，不能重复
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select distinct t_depart from teacher;
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mysql> select distinct t_depart from teacher;
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+-----------------+
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| t_depart |
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+-----------------+
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| 计算机系 |
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| 电子工程系 |
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+-----------------+
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4.筛选出score表中60分到80分的学生
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select * from score where sc_degree between 60 and 80;
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或者
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select * from score where sc_degree > 60 and sc_degree <80;
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mysql> select * from score where sc_degree between 60 and 80;
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+------+-------+-----------+
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| s_no | c_no | sc_degree |
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+------+-------+-----------+
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| 105 | 3-245 | 75 |
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| 105 | 6-166 | 79 |
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| 109 | 3-105 | 76 |
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| 109 | 3-245 | 68 |
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+------+-------+-----------+
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4 rows in set (0.00 sec)
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5.筛选得到85或86或87分的同学
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select * from score where sc_degree = 85 or sc_degree = 86 or sc_degree = 87;
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select * from score where sc_degree in(85,86,87);
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mysql> select * from score where sc_degree = 85 or sc_degree = 86 or sc_degree = 87;
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+------+-------+-----------+
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| s_no | c_no | sc_degree |
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+------+-------+-----------+
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| 103 | 3-245 | 86 |
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| 103 | 6-166 | 85 |
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+------+-------+-----------+
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2 rows in set (0.00 sec)
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6.找到学生，要求班级为95031号或者女生
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select * from student where s_class = 95031 or s_sex = '女';
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mysql> select * from student where s_class = 95031 or s_sex = '女';
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+------+-----------+-------+---------------------+---------+
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| s_no | s_name | s_sex | s_birthday | s_class |
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+------+-----------+-------+---------------------+---------+
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| 102 | 匡明 | 男 | 1975-10-02 00:00:00 | 95031 |
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| 103 | 王丽 | 女 | 1976-01-23 00:00:00 | 95033 |
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| 105 | 王芳 | 女 | 1975-02-10 00:00:00 | 95031 |
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| 106 | 陆军 | 男 | 1974-06-03 00:00:00 | 95031 |
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| 108 | 张全蛋 | 男 | 1975-02-10 00:00:00 | 95031 |
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| 109 | 赵铁柱 | 男 | 1974-06-03 00:00:00 | 95031 |
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+------+-----------+-------+---------------------+---------+
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6 rows in set (0.00 sec)
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```
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## 升降序练习（order by,asc升序 desc）
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```sql
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7.以班级号码倒叙排列所有学生
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select * from student order by s_class desc;
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mysql> select * from student order by s_class desc;
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+------+-----------+-------+---------------------+---------+
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| s_no | s_name | s_sex | s_birthday | s_class |
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+------+-----------+-------+---------------------+---------+
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| 101 | 曾华 | 男 | 1977-09-01 00:00:00 | 95033 |
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| 103 | 王丽 | 女 | 1976-01-23 00:00:00 | 95033 |
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| 104 | 李军 | 男 | 1976-02-20 00:00:00 | 95033 |
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| 107 | 王尼玛 | 男 | 1976-02-20 00:00:00 | 95033 |
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| 102 | 匡明 | 男 | 1975-10-02 00:00:00 | 95031 |
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| 105 | 王芳 | 女 | 1975-02-10 00:00:00 | 95031 |
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| 106 | 陆军 | 男 | 1974-06-03 00:00:00 | 95031 |
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| 108 | 张全蛋 | 男 | 1975-02-10 00:00:00 | 95031 |
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| 109 | 赵铁柱 | 男 | 1974-06-03 00:00:00 | 95031 |
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+------+-----------+-------+---------------------+---------+
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9 rows in set (0.00 sec)
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8.对于成绩，以升序排列班级号码，倒叙排列成绩
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select * from score order by c_no asc,sc_degree desc;
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mysql> select * from score order by c_no asc,sc_degree desc;
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+------+-------+-----------+
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| s_no | c_no | sc_degree |
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+------+-------+-----------+
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| 103 | 3-105 | 92 |
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| 105 | 3-105 | 88 |
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| 109 | 3-105 | 76 |
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| 103 | 3-245 | 86 |
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| 105 | 3-245 | 75 |
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| 109 | 3-245 | 68 |
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| 103 | 6-166 | 85 |
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| 109 | 6-166 | 81 |
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| 105 | 6-166 | 79 |
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+------+-------+-----------+
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9 rows in set (0.00 sec)
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```
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## 统计数量（count）
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```sql
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9.统计班级号为95033的同学总共有多少
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select count(*) from student where s_class='95033';
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mysql> select count(*) from student where s_class='95033';
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+----------+
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| count(*) |
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+----------+
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| 4 |
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+----------+
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1 row in set (0.00 sec)
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```
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## 子查询
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10.求最高分学生的学号和课程编号，max()
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```sql
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select s_no,c_no from score where sc_degree = (select max(sc_degree) from score);
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mysql> select s_no,c_no from score where sc_degree = (select max(sc_degree) from score);
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+------+-------+
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| s_no | c_no |
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+------+-------+
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| 103 | 3-105 |
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+------+-------+
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1 row in set (0.00 sec)
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```
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## 切片（limit）
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```sql
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# 展示成绩表中，倒叙排列成绩，只显示学号和班级号，最后切片，只显示第一个
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select s_no,c_no from score where sc_degree order by sc_degree desc limit 0,1;
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mysql> select s_no,c_no from score where sc_degree order by sc_degree desc limit 0,1;
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+------+-------+
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| s_no | c_no |
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+------+-------+
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| 103 | 3-105 |
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+------+-------+
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1 row in set (0.00 sec)
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```
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## 计算平均成绩（avg,group by）
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```sql
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11.查询每门课的平均成绩
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select c_no,avg(sc_degree) from score group by c_no;
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mysql> select c_no,avg(sc_degree) from score group by c_no;
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+-------+----------------+
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| c_no | avg(sc_degree) |
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+-------+----------------+
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| 3-105 | 85.3333 |
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| 3-245 | 76.3333 |
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| 6-166 | 81.6667 |
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+-------+----------------+
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3 rows in set (0.00 sec)
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```
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## 分组条件及模糊查询（group by having,like）
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```sql
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12.查询score表中至少有两名学生选修并以3开头的课程的平均分数
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|
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select c_no,avg(sc_degree),count(c_no) from score group by c_no
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having count(c_no) >2 and c_no like '3%';
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mysql> select c_no,avg(sc_degree),count(c_no) from score group by c_no
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having count(c_no) >2 and c_no like '3%';
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+-------+----------------+-------------+
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| c_no | avg(sc_degree) | count(c_no) |
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+-------+----------------+-------------+
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| 3-105 | 85.3333 | 3 |
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| 3-245 | 76.3333 | 3 |
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+-------+----------------+-------------+
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||
2 rows in set (0.00 sec)
|
||
```
|
||
|
||
|
||
|
||
## 范围查询（between and）
|
||
|
||
```sql
|
||
13.查询分数大于70，小于90的s_no列
|
||
select s_no,sc_degree from score where sc_degree >70 and sc_degree <90;
|
||
select s_no,sc_degree from score where sc_degree between 70 and 90;
|
||
|
||
mysql> select s_no,sc_degree from score where sc_degree between 70 and 90;
|
||
+------+-----------+
|
||
| s_no | sc_degree |
|
||
+------+-----------+
|
||
| 103 | 86 |
|
||
| 103 | 85 |
|
||
| 105 | 88 |
|
||
| 105 | 75 |
|
||
| 105 | 79 |
|
||
| 109 | 76 |
|
||
| 109 | 81 |
|
||
+------+-----------+
|
||
7 rows in set (0.00 sec)
|
||
```
|
||
|
||
|
||
|
||
## 多表查询(寻找相同条件)
|
||
|
||
```sql
|
||
14. 查询所有学生的s_name\c_no\sc_degree
|
||
select s_name,c_no,sc_degree from student,score where student.s_no=score.s_no;
|
||
```
|
||
|
||
|
||
|
||
```sql
|
||
15.查询所有学生的s_no, c_name, sc_degree列
|
||
select s_no,c_name,sc_degree from score,course where score.c_no=course.c_no;
|
||
mysql> select s_no,c_name,sc_degree from score,course where score.c_no=course.c_no;
|
||
+------+------------+-----------+
|
||
| s_no | c_name | sc_degree |
|
||
+------+------------+-----------+
|
||
| 103 | 计算机导论 | 92 |
|
||
| 103 | 操作系统 | 86 |
|
||
| 103 | 数字电路 | 85 |
|
||
| 105 | 计算机导论 | 88 |
|
||
| 105 | 操作系统 | 75 |
|
||
| 105 | 数字电路 | 79 |
|
||
| 109 | 计算机导论 | 76 |
|
||
| 109 | 操作系统 | 68 |
|
||
| 109 | 数字电路 | 81 |
|
||
+------+------------+-----------+
|
||
9 rows in set (0.03 sec)
|
||
```
|
||
|
||
|
||
|
||
|
||
|
||
## 子查询加分组求平均分(in )
|
||
|
||
```sql
|
||
17. 查询班级是'95031'班学生每门课的平均分
|
||
select avg(sc_degree) from score
|
||
where s_no in (select s_no from student where s_class='95031') group by c_no;
|
||
```
|
||
|
||
## 子查询深入
|
||
|
||
```sql
|
||
18. 查询选修"3-105"课程的成绩高于'109'分同学'3-105'成绩 的所有同学的记录
|
||
(在大家都在选修3-105的背景下 查询 所有 分数 比 学号为"109"还要高的学生信息)
|
||
select * from score where c_no='3-105' and sc_degree >
|
||
(select sc_degree from score where c_no='3-105' and s_no='109');
|
||
|
||
mysql> select * from score where c_no='3-105' and sc_degree >
|
||
-> (select sc_degree from score where c_no='3-105' and s_no='109');
|
||
+------+-------+-----------+
|
||
| s_no | c_no | sc_degree |
|
||
+------+-------+-----------+
|
||
| 103 | 3-105 | 92 |
|
||
| 105 | 3-105 | 88 |
|
||
+------+-------+-----------+
|
||
2 rows in set (0.00 sec)
|
||
19.查询成绩高于学号为'109',课程号为'3-105'的成绩的所有记录
|
||
(不管哪门课，只要比那个分数高就行)
|
||
select * from score where sc_degree >
|
||
(select sc_degree from score where c_no='3-105' and s_no='109');
|
||
|
||
mysql> select * from score where sc_degree > (select sc_degree from score where c_no='3-105' and s_no='109');
|
||
+------+-------+-----------+
|
||
| s_no | c_no | sc_degree |
|
||
+------+-------+-----------+
|
||
| 103 | 3-105 | 92 |
|
||
| 103 | 3-245 | 86 |
|
||
| 103 | 6-166 | 85 |
|
||
| 105 | 3-105 | 88 |
|
||
| 105 | 6-166 | 79 |
|
||
| 109 | 6-166 | 81 |
|
||
+------+-------+-----------+
|
||
6 rows in set (0.00 sec)
|
||
```
|
||
|
||
## 年份函数(year)
|
||
|
||
```sql
|
||
20.查询所有学号为108.101的同学同年出生的所有学生的s_no,s_name和s_birthday
|
||
select s_no,s_name,s_birthday from student
|
||
where year(s_birthday) in (select year(s_birthday) from student where s_no in (101,108));
|
||
|
||
mysql> select s_no,s_name,s_birthday from student
|
||
-> where year(s_birthday) in (select year(s_birthday) from student where s_no in (101,108));
|
||
+------+--------+---------------------+
|
||
| s_no | s_name | s_birthday |
|
||
+------+--------+---------------------+
|
||
| 101 | 曾华 | 1977-09-01 00:00:00 |
|
||
| 102 | 匡明 | 1975-10-02 00:00:00 |
|
||
| 105 | 王芳 | 1975-02-10 00:00:00 |
|
||
| 108 | 张全蛋 | 1975-02-10 00:00:00 |
|
||
+------+--------+---------------------+
|
||
```
|
||
|
||
## 嵌套子查询
|
||
|
||
```sql
|
||
21. 查询张旭老师上的课的学生的成绩
|
||
select t_no from teacher where t_name = '张旭';
|
||
select c_no from class where t_no = (select t_no from teacher where t_name = '张旭');
|
||
select * from score where c_no =(select c_no from course where t_no = (select t_no from teacher where t_name = '张旭'));
|
||
```
|
||
|
||
|
||
|
||
## in的使用
|
||
|
||
```sql
|
||
23.查询班级号为95033,95031的学生，并且倒叙排序
|
||
select * from student where s_class in (95033,95031) order by s_class;
|
||
|
||
mysql> select * from student where s_class in (95033,95031) order by s_class;
|
||
+------+--------+-------+---------------------+---------+
|
||
| s_no | s_name | s_sex | s_birthday | s_class |
|
||
+------+--------+-------+---------------------+---------+
|
||
| 102 | 匡明 | 男 | 1975-10-02 00:00:00 | 95031 |
|
||
| 105 | 王芳 | 女 | 1975-02-10 00:00:00 | 95031 |
|
||
| 106 | 陆军 | 男 | 1974-06-03 00:00:00 | 95031 |
|
||
| 108 | 张全蛋 | 男 | 1975-02-10 00:00:00 | 95031 |
|
||
| 109 | 赵铁柱 | 男 | 1974-06-03 00:00:00 | 95031 |
|
||
| 101 | 曾华 | 男 | 1977-09-01 00:00:00 | 95033 |
|
||
| 103 | 王丽 | 女 | 1976-01-23 00:00:00 | 95033 |
|
||
| 104 | 李军 | 男 | 1976-02-20 00:00:00 | 95033 |
|
||
| 107 | 王尼玛 | 男 | 1976-02-20 00:00:00 | 95033 |
|
||
+------+--------+-------+---------------------+---------+
|
||
9 rows in set (0.00 sec)
|
||
```
|
||
|
||
|
||
|
||
```sql
|
||
24. 查询存在85分以上成绩的课程c_no
|
||
select c_no from score where sc_degree >85;
|
||
|
||
mysql> select c_no from score where sc_degree >85;
|
||
+-------+
|
||
| c_no |
|
||
+-------+
|
||
| 3-105 |
|
||
| 3-105 |
|
||
| 3-105 |
|
||
| 3-245 |
|
||
| 3-105 |
|
||
| 3-105 |
|
||
+-------+
|
||
6 rows in set (0.00 sec)
|
||
```
|
||
|
||
## 综合使用
|
||
|
||
```sql
|
||
25.查出所有'计算机系' 教师所教课程的成绩表
|
||
select t_no from teacher where t_depart='计算机系';
|
||
select c_no from course where t_no in (select t_no from teacher where t_depart='计算机系');
|
||
select * from score where c_no in(select c_no from course where t_no in (select t_no from teacher where t_depart='计算机系'));
|
||
|
||
mysql> select * from score where c_no in(select c_no from course where t_no in (select t_no from teacher where t_depart='计算机系'));
|
||
+------+-------+-----------+
|
||
| s_no | c_no | sc_degree |
|
||
+------+-------+-----------+
|
||
| 103 | 3-245 | 86 |
|
||
| 105 | 3-245 | 75 |
|
||
| 109 | 3-245 | 68 |
|
||
| 101 | 3-105 | 90 |
|
||
| 102 | 3-105 | 91 |
|
||
| 103 | 3-105 | 92 |
|
||
| 104 | 3-105 | 89 |
|
||
| 105 | 3-105 | 88 |
|
||
| 109 | 3-105 | 76 |
|
||
+------+-------+-----------+
|
||
9 rows in set (0.00 sec)
|
||
```
|
||
|
||
## 求并集操作(union)
|
||
|
||
```sql
|
||
26.查询'计算机系'与'电子工程系' 不同职称的教师的t_name和rof
|
||
select * from teacher where t_depart='计算机系'
|
||
and t_rof not in (select t_rof from teacher where t_depart='电子工程系')
|
||
union
|
||
select * from teacher where t_depart='电子工程系'
|
||
and t_rof not in (select t_rof from teacher where t_depart='计算机系');
|
||
|
||
mysql> select * from teacher where t_depart='计算机系' and t_rof not in (select t_rof from teacher where t_depart='电子 工程系')
|
||
-> union
|
||
-> select * from teacher where t_depart='电子工程系' and t_rof not in (select t_rof from teacher where t_depart='计 算机系');
|
||
+------+--------+-------+---------------------+--------+------------+
|
||
| t_no | t_name | t_sex | t_birthday | t_rof | t_depart |
|
||
+------+--------+-------+---------------------+--------+------------+
|
||
| 804 | 李诚 | 男 | 1958-12-02 00:00:00 | 副教授 | 计算机系 |
|
||
| 856 | 张旭 | 男 | 1969-03-12 00:00:00 | 讲师 | 电子工程系 |
|
||
+------+--------+-------+---------------------+--------+------------+
|
||
2 rows in set (0.00 sec)
|
||
|
||
严格正确版：
|
||
select t_name,t_rof from teacher where t_depart='计算机系'
|
||
and t_rof not in (select t_rof from teacher where t_depart='电子工程系')
|
||
union
|
||
select t_name,t_rof from teacher where t_depart='电子工程系'
|
||
and t_rof not in (select t_rof from teacher where t_depart='计算机系');
|
||
|
||
+--------+--------+
|
||
| t_name | t_rof |
|
||
+--------+--------+
|
||
| 李诚 | 副教授 |
|
||
| 张旭 | 讲师 |
|
||
+--------+--------+
|
||
2 rows in set (0.00 sec)
|
||
```
|
||
|
||
|
||
|
||
## 多个值比较多个值：至少（any）
|
||
|
||
```sql
|
||
27, 查询选修编号为"3-105"课程且成绩至少高于选修编号为'3-245'同学的c_no,s_no和sc_degree,并且按照sc_degree从高到地次序排序
|
||
|
||
select c_no,s_no,sc_degree from score where c_no='3-105' and sc_degree > any(select sc_degree from score where c_no='3-245') order by sc_degree desc;
|
||
|
||
+-------+------+-----------+
|
||
| c_no | s_no | sc_degree |
|
||
+-------+------+-----------+
|
||
| 3-105 | 103 | 92 |
|
||
| 3-105 | 102 | 91 |
|
||
| 3-105 | 101 | 90 |
|
||
| 3-105 | 104 | 89 |
|
||
| 3-105 | 105 | 88 |
|
||
| 3-105 | 109 | 76 |
|
||
+-------+------+-----------+
|
||
6 rows in set (0.00 sec)
|
||
```
|
||
|
||
|
||
|
||
## 多个值比较多个值：所有（all）
|
||
|
||
```sql
|
||
28.查询选修编号为"3-105"且成绩高于选修编号为"3-245"课程的同学c_no.s_no和sc_degree
|
||
select c_no,s_no,sc_degree from score where c_no='3-105' and sc_degree > all(select sc_degree from score where c_no='3-245');
|
||
+-------+------+-----------+
|
||
| c_no | s_no | sc_degree |
|
||
+-------+------+-----------+
|
||
| 3-105 | 101 | 90 |
|
||
| 3-105 | 102 | 91 |
|
||
| 3-105 | 103 | 92 |
|
||
| 3-105 | 104 | 89 |
|
||
| 3-105 | 105 | 88 |
|
||
+-------+------+-----------+
|
||
5 rows in set (0.00 sec)
|
||
```
|
||
|
||
## 使用别名(as)
|
||
|
||
```sql
|
||
29.查询所有教师和同学的 name ,sex, birthday
|
||
select s_name as name,s_sex as sex,s_birthday as birthday from student
|
||
union
|
||
select t_name as name,t_sex as sex,t_birthday as birthday from teacher;
|
||
|
||
mysql> select s_name as name,s_sex as sex,s_birthday as birthday from student
|
||
-> union
|
||
-> select t_name as name,t_sex as sex,t_birthday as birthday from teacher;
|
||
+--------+-----+---------------------+
|
||
| name | sex | birthday |
|
||
+--------+-----+---------------------+
|
||
| 曾华 | 男 | 1977-09-01 00:00:00 |
|
||
| 匡明 | 男 | 1975-10-02 00:00:00 |
|
||
| 王丽 | 女 | 1976-01-23 00:00:00 |
|
||
| 李军 | 男 | 1976-02-20 00:00:00 |
|
||
| 王芳 | 女 | 1975-02-10 00:00:00 |
|
||
| 陆军 | 男 | 1974-06-03 00:00:00 |
|
||
| 王尼玛 | 男 | 1976-02-20 00:00:00 |
|
||
| 张全蛋 | 男 | 1975-02-10 00:00:00 |
|
||
| 赵铁柱 | 男 | 1974-06-03 00:00:00 |
|
||
| 李诚 | 男 | 1958-12-02 00:00:00 |
|
||
| 王萍 | 女 | 1972-05-05 00:00:00 |
|
||
| 刘冰 | 女 | 1977-08-14 00:00:00 |
|
||
| 张旭 | 男 | 1969-03-12 00:00:00 |
|
||
+--------+-----+---------------------+
|
||
30.查询所有'女'教师和'女'学生的name,sex,birthday
|
||
select s_name as name,s_sex as sex,s_birthday as birthday from student where s_sex='女'
|
||
union
|
||
select t_name as name,t_sex as sex,t_birthday as birthday from teacher where t_sex='女';
|
||
|
||
+------+-----+---------------------+
|
||
| name | sex | birthday |
|
||
+------+-----+---------------------+
|
||
| 王丽 | 女 | 1976-01-23 00:00:00 |
|
||
| 王芳 | 女 | 1975-02-10 00:00:00 |
|
||
| 王萍 | 女 | 1972-05-05 00:00:00 |
|
||
| 刘冰 | 女 | 1977-08-14 00:00:00 |
|
||
+------+-----+---------------------+
|
||
4 rows in set (0.00 sec)
|
||
```
|
||
|
||
## 复制表数据作条件查询(别名的使用)
|
||
|
||
```sql
|
||
31. 查询成绩比该课程平均成绩低的同学的成绩表
|
||
|
||
select * from score a where sc_degree < (select avg(sc_degree) from score b where a.c_no=b.c_no);
|
||
|
||
+------+-------+-----------+
|
||
| s_no | c_no | sc_degree |
|
||
+------+-------+-----------+
|
||
| 105 | 3-245 | 75 |
|
||
| 105 | 6-166 | 79 |
|
||
| 109 | 3-105 | 76 |
|
||
| 109 | 3-245 | 68 |
|
||
| 109 | 6-166 | 81 |
|
||
+------+-------+-----------+
|
||
5 rows in set (0.01 sec)
|
||
```
|
||
|
||
|
||
|
||
```sql
|
||
32.查询所有任课教师的t_name 和 t_depart(要在分数表中可以查得到)
|
||
select t_name,t_depart from teacher where t_no in (select t_no from course);
|
||
|
||
+--------+------------+
|
||
| t_name | t_depart |
|
||
+--------+------------+
|
||
| 李诚 | 计算机系 |
|
||
| 王萍 | 计算机系 |
|
||
| 刘冰 | 电子工程系 |
|
||
| 张旭 | 电子工程系 |
|
||
+--------+------------+
|
||
4 rows in set (0.02 sec)
|
||
```
|
||
|
||
## 条件加分组查询
|
||
|
||
```sql
|
||
33.查出至少有2名男生的班号
|
||
select s_class from student group by s_class having count(s_sex='男')>1;
|
||
select s_class from student where s_sex='男' group by s_class having count(s_no)>1;
|
||
|
||
mysql> select s_class from student where s_sex='男' group by s_class having count(s_no)>1;
|
||
+---------+
|
||
| s_class |
|
||
+---------+
|
||
| 95033 |
|
||
| 95031 |
|
||
+---------+
|
||
2 rows in set (0.00 sec)
|
||
```
|
||
|
||
## 模糊查询取反(not like,%)
|
||
|
||
```sql
|
||
34. 查询student 表中不姓"王"的同学的记录
|
||
select * from student where s_name not like '王%';
|
||
|
||
+------+--------+-------+---------------------+---------+
|
||
| s_no | s_name | s_sex | s_birthday | s_class |
|
||
+------+--------+-------+---------------------+---------+
|
||
| 101 | 曾华 | 男 | 1977-09-01 00:00:00 | 95033 |
|
||
| 102 | 匡明 | 男 | 1975-10-02 00:00:00 | 95031 |
|
||
| 104 | 李军 | 男 | 1976-02-20 00:00:00 | 95033 |
|
||
| 106 | 陆军 | 男 | 1974-06-03 00:00:00 | 95031 |
|
||
| 108 | 张全蛋 | 男 | 1975-02-10 00:00:00 | 95031 |
|
||
| 109 | 赵铁柱 | 男 | 1974-06-03 00:00:00 | 95031 |
|
||
+------+--------+-------+---------------------+---------+
|
||
6 rows in set (0.00 sec)
|
||
```
|
||
|
||
|
||
|
||
## 计算年龄大小(year(now()))
|
||
|
||
```sql
|
||
35. 查询student 中每个学生的姓名和年龄(当前时间 - 出生年份)
|
||
|
||
select s_name,year(now())-year(s_birthday) as age from student;
|
||
+--------+------+
|
||
| s_name | age |
|
||
+--------+------+
|
||
| 曾华 | 43 |
|
||
| 匡明 | 45 |
|
||
| 王丽 | 44 |
|
||
| 李军 | 44 |
|
||
| 王芳 | 45 |
|
||
| 陆军 | 46 |
|
||
| 王尼玛 | 44 |
|
||
| 张全蛋 | 45 |
|
||
| 赵铁柱 | 46 |
|
||
+--------+------+
|
||
```
|
||
|
||
## 最大值最小值（min,max）
|
||
|
||
```sql
|
||
36. 查询student中最大和最小的 s_birthday的值
|
||
select min(s_birthday),max(s_birthday) from student;
|
||
+---------------------+---------------------+
|
||
| min(s_birthday) | max(s_birthday) |
|
||
+---------------------+---------------------+
|
||
| 1974-06-03 00:00:00 | 1977-09-01 00:00:00 |
|
||
+---------------------+---------------------+
|
||
1 row in set (0.00 sec)
|
||
```
|
||
|
||
## 多字段排序
|
||
|
||
```sql
|
||
37. 以班级号和年龄从大到小的顺序查询student表中的全部记录
|
||
select * from student order by s_class desc and s_birthday;
|
||
+------+--------+-------+---------------------+---------+
|
||
| s_no | s_name | s_sex | s_birthday | s_class |
|
||
+------+--------+-------+---------------------+---------+
|
||
| 101 | 曾华 | 男 | 1977-09-01 00:00:00 | 95033 |
|
||
| 102 | 匡明 | 男 | 1975-10-02 00:00:00 | 95031 |
|
||
| 103 | 王丽 | 女 | 1976-01-23 00:00:00 | 95033 |
|
||
| 104 | 李军 | 男 | 1976-02-20 00:00:00 | 95033 |
|
||
| 105 | 王芳 | 女 | 1975-02-10 00:00:00 | 95031 |
|
||
| 106 | 陆军 | 男 | 1974-06-03 00:00:00 | 95031 |
|
||
| 107 | 王尼玛 | 男 | 1976-02-20 00:00:00 | 95033 |
|
||
| 108 | 张全蛋 | 男 | 1975-02-10 00:00:00 | 95031 |
|
||
| 109 | 赵铁柱 | 男 | 1974-06-03 00:00:00 | 95031 |
|
||
+------+--------+-------+---------------------+---------+
|
||
9 rows in set (0.00 sec)
|
||
```
|
||
|
||
## 子查询练习
|
||
|
||
```sql
|
||
38. 查询"男"教师 及其所上的课
|
||
select t_no from teacher where t_sex='男';
|
||
select * from course where t_no in (select t_no from teacher where t_sex='男');
|
||
|
||
mysql> select * from course where t_no in (select t_no from teacher where t_sex='男');
|
||
+-------+----------+------+
|
||
| c_no | c_name | t_no |
|
||
+-------+----------+------+
|
||
| 3-245 | 操作系统 | 804 |
|
||
| 6-166 | 数字电路 | 856 |
|
||
+-------+----------+------+
|
||
2 rows in set (0.00 sec)
|
||
39.查询最高分同学的s_no c_no 和 sc_degree;
|
||
select max(sc_degree) from score;
|
||
select * from score where sc_degree =(select max(sc_degree) from score);
|
||
+------+-------+-----------+
|
||
| s_no | c_no | sc_degree |
|
||
+------+-------+-----------+
|
||
| 103 | 3-105 | 92 |
|
||
+------+-------+-----------+
|
||
1 row in set (0.00 sec)
|
||
```
|
||
|
||
|
||
|
||
```sql
|
||
40. 查询和"李军"同性别的所有同学的s_name
|
||
select s_name from student where s_sex = (select s_sex from student where s_name='李军');
|
||
|
||
mysql> select s_name from student where s_sex = (select s_sex from student where s_name='李军');
|
||
+--------+
|
||
| s_name |
|
||
+--------+
|
||
| 曾华 |
|
||
| 匡明 |
|
||
| 李军 |
|
||
| 陆军 |
|
||
| 王尼玛 |
|
||
| 张全蛋 |
|
||
| 赵铁柱 |
|
||
+--------+
|
||
7 rows in set (0.00 sec)
|
||
41.查询和"李军"同性别并且同班的所有同学的s_name
|
||
SELECT s_name, s_sex FROM student WHERE s_sex = (SELECT s_sex FROM student WHERE s_name = '李军') AND s_class = (SELECT s_class FROM student WHERE s_name = '李军');
|
||
+--------+
|
||
| s_name |
|
||
+--------+
|
||
| 曾华 |
|
||
| 李军 |
|
||
| 王尼玛 |
|
||
+--------+
|
||
3 rows in set (0.00 sec)
|
||
```
|
||
|
||
|
||
|
||
```sql
|
||
42. 查询所有选修'计算机导论'课程的'男'同学的成绩表
|
||
select c_no from course where c_name='计算机导论';
|
||
select s_no from student where s_sex='男'；
|
||
select * from score where s_no in (select s_no from student where s_sex='男') and
|
||
c_no in (select c_no from course where c_name='计算机导论');
|
||
|
||
+------+-------+-----------+
|
||
| s_no | c_no | sc_degree |
|
||
+------+-------+-----------+
|
||
| 101 | 3-105 | 90 |
|
||
| 102 | 3-105 | 91 |
|
||
| 104 | 3-105 | 89 |
|
||
| 109 | 3-105 | 76 |
|
||
+------+-------+-----------+
|
||
4 rows in set (0.00 sec)
|
||
```
|
||
|
||
# 连接查询
|
||
|
||
|
||
|
||
左外连接
|
||
|
||
左连接
|
||
|
||
全连接
|
||
|
||
**两张表都没有出现交集的数据集**
|
||
|
||
右连接
|
||
|
||
右外连接
|
||
|
||
内连接
|
||
|
||
## 连接查询案例
|
||
|
||
## 内连接（inner join …… on）
|
||
|
||
```sql
|
||
mysql> create table card(
|
||
-> id int,
|
||
-> name varchar(20)
|
||
-> );
|
||
|
||
insert into card values(1,'饭卡');
|
||
insert into card values(2,'建行卡');
|
||
insert into card values(3,'农行卡');
|
||
insert into card values(4,'工商卡');
|
||
insert into card values(5,'邮政卡');
|
||
```
|
||
|
||
|
||
|
||
```sql
|
||
mysql> create table person(
|
||
-> id int,
|
||
-> name varchar(20),
|
||
-> cardId int);
|
||
|
||
insert into person values(1,'张三',1);
|
||
insert into person values(2,'李四',3);
|
||
insert into person values(3,'王五',6);
|
||
```
|
||
|
||
**person表:**
|
||
|
||
```sql
|
||
mysql> select * from person;
|
||
+------+--------+--------+
|
||
| id | name | cardId |
|
||
+------+--------+--------+
|
||
| 1 | 张三 | 1 |
|
||
| 2 | 李四 | 3 |
|
||
| 3 | 王五 | 6 |
|
||
+------+--------+--------+
|
||
3 rows in set (0.00 sec)
|
||
```
|
||
|
||
**card表:**
|
||
|
||
```sql
|
||
mysql> select * from card;
|
||
+------+-----------+
|
||
| id | name |
|
||
+------+-----------+
|
||
| 1 | 饭卡 |
|
||
| 2 | 建行卡 |
|
||
| 3 | 农行卡 |
|
||
| 4 | 工商卡 |
|
||
| 5 | 邮政卡 |
|
||
+------+-----------+
|
||
5 rows in set (0.00 sec)
|
||
```
|
||
|
||
### 内连接查询
|
||
|
||
```sql
|
||
select * from person inner join card on person.cardId=card.id;
|
||
+------+------+--------+------+--------+
|
||
| id | name | cardId | id | name |
|
||
+------+------+--------+------+--------+
|
||
| 1 | 张三 | 1 | 1 | 饭卡 |
|
||
| 2 | 李四 | 3 | 3 | 农行卡 |
|
||
+------+------+--------+------+--------+
|
||
2 rows in set (0.00 sec)
|
||
```
|
||
|
||
整个查询的执行过程如下:
|
||
|
||
1. 从 `person` 表中选取所有记录
|
||
2. 对于每个 `person` 记录,查找 `card` 表中 `id` 字段与 `person.cardId` 相匹配的记录
|
||
3. 将匹配的 `person` 和 `card` 记录组合成一条结果记录返回
|
||
|
||
## 外连接
|
||
|
||
### 左外连接(left join ...... on)
|
||
|
||
左外连接会把左边的表的数据全部取出来 ，右边表如果没有就用NULL补上
|
||
|
||
```sql
|
||
mysql> select * from person left join card on person.cardId=card.id;
|
||
+------+------+--------+------+--------+
|
||
| id | name | cardId | id | name |
|
||
+------+------+--------+------+--------+
|
||
| 1 | 张三 | 1 | 1 | 饭卡 |
|
||
| 2 | 李四 | 3 | 3 | 农行卡 |
|
||
| 3 | 王五 | 6 | NULL | NULL |
|
||
+------+------+--------+------+--------+
|
||
3 rows in set (0.00 sec)
|
||
```
|
||
|
||
整个查询的执行过程如下:
|
||
|
||
1. 从 `person` 表中选取所有记录
|
||
2. 对于每个 `person` 记录,查找 `card` 表中 `id` 字段与 `person.cardId` 相匹配的记录
|
||
3. 将匹配的 `person` 和 `card` 记录组合成一条结果记录返回
|
||
4. 对于无法匹配的 `person` 记录,用 `NULL` 填充 `card` 表的字段
|
||
|
||
### 右外连接(right join ...... on)
|
||
|
||
右外连接会把左边的表的数据全部取出来，左边表如果没有就用NULL补上
|
||
|
||
```sql
|
||
mysql> select * from person right join card on person.cardId=card.id;
|
||
+------+------+--------+------+--------+
|
||
| id | name | cardId | id | name |
|
||
+------+------+--------+------+--------+
|
||
| 1 | 张三 | 1 | 1 | 饭卡 |
|
||
| NULL | NULL | NULL | 2 | 建行卡 |
|
||
| 2 | 李四 | 3 | 3 | 农行卡 |
|
||
| NULL | NULL | NULL | 4 | 工商卡 |
|
||
| NULL | NULL | NULL | 5 | 邮政卡 |
|
||
+------+------+--------+------+--------+
|
||
5 rows in set (0.00 sec)
|
||
```
|
||
|
||
整个查询的执行过程如下:
|
||
|
||
1. 从 `card` 表中选取所有记录
|
||
2. 对于每个 `card` 记录,查找 `person` 表中 `cardId` 字段与 `card.id` 相匹配的记录
|
||
3. 将匹配的 `person` 和 `card` 记录组合成一条结果记录返回
|
||
4. 对于无法匹配的 `card` 记录,用 `NULL` 填充 `person` 表的字段
|
||
|
||
### 全连接（full join）
|
||
|
||
```sql
|
||
select * from person full join card on person.cardId=card.id;
|
||
|
||
mysql不支持全连接，换一种方式表达
|
||
|
||
select * from person left join card on person.cardId=card.id union select * from person right join card on person.cardId=card.id;
|
||
+------+------+--------+------+--------+
|
||
| id | name | cardId | id | name |
|
||
+------+------+--------+------+--------+
|
||
| 1 | 张三 | 1 | 1 | 饭卡 |
|
||
| 2 | 李四 | 3 | 3 | 农行卡 |
|
||
| 3 | 王五 | 6 | NULL | NULL |
|
||
| NULL | NULL | NULL | 2 | 建行卡 |
|
||
| NULL | NULL | NULL | 4 | 工商卡 |
|
||
| NULL | NULL | NULL | 5 | 邮政卡 |
|
||
+------+------+--------+------+--------+
|
||
6 rows in set (0.00 sec)
|
||
```
|
||
|
||
整个查询的执行过程如下:
|
||
|
||
1. 从 `person` 表和 `card` 表中选取所有记录
|
||
2. 对于每个 `person` 记录,查找 `card` 表中 `id` 字段与 `person.cardId` 相匹配的记录
|
||
3. 对于每个 `card` 记录,查找 `person` 表中 `cardId` 字段与 `card.id` 相匹配的记录
|
||
4. 将匹配的 `person` 和 `card` 记录组合成一条结果记录返回
|
||
5. 对于无法匹配的记录,用 `NULL` 填充相应的字段 |