整理MySQL数据库查询语句的相关使用笔记，首先准备查询数据，以下准备了四张表，表结构如下：
| students(学生表) | teacher（教师表） | course（课程表） | score(成绩表) |
| --学号 --姓名 --性别 --出生年月日 --班级编号 |
--教师编号 --教师名称 --教师性别 --出生年月日 --职称 --所在部门 |
--课程号 --课程名 --教师编号 |
--学号 --课程号 --成绩 |
| create table students( sno varchar(20) primary key, sname varchar(20) not null, ssex varchar(10) not null, birthday datetime, class varchar(20) ) default character set = 'utf8'; |
create table teacher( tno varchar(20) primary key, tname varchar(20)not null, tsex varchar(10) not null, tbirthday datetime, prof varchar(20) not null, tdepar varchar(20)not null )default character set = 'utf8'; |
create table course( cno varchar(20) primary key, cname varchar(20)not null, tno varchar(20), foreign key(tno) references teacher(tno) )default character set = 'utf8'; |
create table score( sno varchar(20) not null, cno varchar(20) not null, degree decimal, foreign key(sno) references students(sno), foreign key(cno) references course(cno), primary key(sno,cno) )default character set = 'utf8'; |
首先，创建一个数据库，任意取名
mysql> create database chennuan;
Query OK, 1 row affected (0.00 sec)
切换数据库
mysql> use chennuan;
Database changed
创建学生表：
create table students(
sno varchar(20) primary key,
sname varchar(20) not null,
ssex varchar(10) not null,
birthday datetime,
class varchar(20)
) default character set = 'utf8';创建教师表
create table teacher(
tno varchar(20) primary key,
tname varchar(20)not null,
tsex varchar(10) not null,
tbirthday datetime,
prof varchar(20) not null,
tdepar varchar(20)not null
)default character set = 'utf8';创建课程表：
create table course(
cno varchar(20) primary key,
cname varchar(20)not null,
tno varchar(20),
foreign key(tno) references teacher(tno)
)default character set = 'utf8';
Query OK, 0 rows affected (0.02 sec)
创建成绩表：
create table score(
sno varchar(20) not null,
cno varchar(20) not null,
degree decimal,
foreign key(sno) references students(sno),
foreign key(cno) references course(cno),
primary key(sno,cno)
)default character set = 'utf8';查看创建的表
mysql> show tables;
+--------------------+
| Tables_in_chennuan |
+--------------------+
| course |
| score |
| students |
| teacher |
+--------------------+
4 rows in set (0.00 sec)
添加学生表数据
insert into students values('101','张三','男','1977-09-01','95033');
insert into students values('102','李四','男','1975-10-02','95031');
insert into students values('103','王五','女','1976-01-23','95033');
insert into students values('104','铁柱','男','1976-02-20','95033');
insert into students values('105','小丽','女','1975-02-10','95031');
insert into students values('106','小红','男','1974-06-03','95031');
insert into students values('107','小绿','男','1976-02-20','95033');
insert into students values('108','大妞','女','1975-02-10','95031');
insert into students values('109','乖乖','男','1974-06-03','95031');添加教师表数据：
insert into teacher values('804','李想','男','1958-06-03','副教授','计算机系');
insert into teacher values('856','张丹','男','1969-02-20','讲师','电子工程系');
insert into teacher values('825','王超','女','1970-02-10','助教','计算机系');
insert into teacher values('831','刘能','女','1961-06-03','助教','电子工程系');添加课程表数据：
insert into course values('3-105','计算机导论','825');
insert into course values('3-245','操作系统','804');
insert into course values('6-166','数字电路','856');
insert into course values('9-888','高等数学','831');添加成绩表数据：
insert into score values('103','3-105','92');
insert into score values('103','3-245','86');
insert into score values('103','6-166','85');
insert into score values('105','3-105','88');
insert into score values('105','3-245','75');
insert into score values('105','6-166','79');
insert into score values('109','3-105','76');
insert into score values('109','3-245','68');
insert into score values('109','6-166','81');FAQ
问题一：
mysql> insert into students values('1','zhang','男','1991-01-02','20');
ERROR 1366 (HY000): Incorrect string value: '\xE7\x94\xB7' for column 'ssex' at row 1
原因为，数据库没有设置字符集为utf8，修改方法参考该文档
//查询表的字符集
mysql> show create table students;
+----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| students | CREATE TABLE `students` (
`sno` varchar(20) CHARACTER SET latin1 NOT NULL,
`sname` varchar(20) CHARACTER SET latin1 NOT NULL,
`ssex` varchar(10) CHARACTER SET latin1 NOT NULL,
`birthday` datetime DEFAULT NULL,
`class` varchar(20) CHARACTER SET latin1 DEFAULT NULL,
PRIMARY KEY (`sno`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+----------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
//修改表字段字符集
alter table students change sno sno varchar(20) CHARACTER SET utf8 NOT NULL;
//查询数据库字符集
mysql> show variables like '%char%';
+--------------------------------------+----------------------------+
| Variable_name | Value |
+--------------------------------------+----------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | latin1 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | utf8 |
| character_set_system | utf8 |
| character_sets_dir | /usr/share/mysql/charsets/ |
| validate_password_special_char_count | 1 |
+--------------------------------------+----------------------------+
9 rows in set (0.02 sec)
https://blog.csdn.net/qq_31683121/article/details/73371697
参考：
感谢code 158编程俱乐部
