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四个常用的语句查询 : insert delete update select
insert into student(Sno,name) values(95001,张三)
delete from student where name张三
upda… 文章目录 增删改查解决数据库不能存储中文问题创建表数据类型表的基本操作主键唯一键 unique外键实战 增删改查
四个常用的语句查询 : insert delete update select
insert into student(Sno,name) values(95001,张三)
delete from student where name张三
update student set name李四 where sno 95001
select sno,name from student
mysql select * from student;
--------------
| sno | name |
--------------
| 95001 | sdgge |
| 95002 | tomas |
--------------
2 rows in set (0.00 sec)mysql select * from student;
--------------
| sno | name |
--------------
| 95001 | sdgge |
| 95002 | tomas |
--------------
2 rows in set (0.00 sec)mysql insert into student values(95003,1faf);
Query OK, 1 row affected (0.01 sec)mysql select * from student;
--------------
| sno | name |
--------------
| 95001 | sdgge |
| 95002 | tomas |
| 95003 | 1faf |
--------------
3 rows in set (0.01 sec)mysql update student set namegsd where sno95003;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0mysql select * from student;
--------------
| sno | name |
--------------
| 95001 | sdgge |
| 95002 | tomas |
| 95003 | gsd |
--------------
3 rows in set (0.00 sec)
mysql delete from student where sno95002;
Query OK, 1 row affected (0.00 sec)mysql select * from student;
--------------
| sno | name |
--------------
| 95001 | sdgge |
| 95003 | gsd |
--------------
2 rows in set (0.00 sec)解决数据库不能存储中文问题
create database testdb default character set utf8 collate utf8_general_ci;
查看数据当前用的哪个编码
mysql show variables like character_set_database;
---------------------------------
| Variable_name | Value |
---------------------------------
| character_set_database | utf8mb3 |
---------------------------------
1 row in set (0.01 sec)mysql alter database testdb chatacter set utf8;
只影响之后创建的表或者问chatgpt创建表
创建表create table
mysql create table student- (- sno int,- name varchar(10),- gender varchar(10),- birtthday date,- mobile varchar(20),- email varchar(50),- homeaddress varchar(100)- );
Query OK, 0 rows affected (0.05 sec)# 创建一个表Book
create table book
(BookId int,BookName varchar(100),Author varchar(20),Press varchar(100),Price float(6,2)
)
下图显示的是如何用navicat进行命令进行查询语句 数据类型
如下图所示
使用的类型要满足你用的大小
尽量节约空间字符串 长度明确的用 char
不明确的用varchar表的基本操作
create table if not exists student
(
SNO int UNSIGNED,
SName varchar(20),
Gender char(3),
Mobile char(11),
Email varchar(100),
Adress varchar(200)
)#修改表
alter table student add column studentdesc TEXT# 删除表
drop table student 插入一些数据
INSERT INTO student(SNO, SName, Gender, Mobile, Email, Adress) VALUES (95001, 张三, 男, 1283833333, abcgmail.com, 上海市某某路);插入多行
INSERT INTO student(SNO, SName, Gender, Mobile, Email, Adress)
VALUES (95001, 张三, 男, 1283833333, abcgmail.com, 上海市某某路),(95002, 李四, 男, 1383833333, defgmail.com, 北京市某某路),(95003, 王五, 女, 1483833333, ghigmail.com, 广州市某某路),(95004, 赵六, 女, 1583833333, jklgmail.com, 深圳市某某路),(95005, 钱七, 男, 1683833333, mnogmail.com, 成都市某某路);修改一条记录
UPdate student set Gender男 where SNO95001 Or Sname张三
update student set Gender女 # 这句话会修改所有的删除
delete from student where Gender女;查询
select * from student;
select SNo,SName where Mobile like %888主键
上面表中SNO 有重复的 对于关键字段不能保持唯一主键可以做到
主键要唯一且不能为空主键只能有一个
create table student01
(
SNO int PRIMARY key,
SName varchar(20)
)或者一般用这种这种有名字方便管理
create table student02
(
SNO int,
Sname varchar(20),
CONSTRAINT Pk_SNO PRIMARY Key(SNO)
)复合主键
create table borrowbook
(
sno int,
bookid int,
borrowdata date,
returndata date,
constraint pk_borrowbook primary key(sno,bookid)
)
需要两个行来一起捆绑一起来进行判断唯一键 unique
保证字段的值不能重复因为一个表只能有一个主键其他的字段如果也想唯一则需要唯一键
一个表中可以为多个
create table student03
(
sno int,
sname varchar(20) not null,
gender char(3),
birthday date,
mobile varchar(20),
email varchar(100),
address varchar(200),
constraint pk_sno primary key(sno),
constraint uq_mobile unique(mobile),
constraint uq_email unique(email)
)插入10条数据
INSERT INTO student03 (sno, sname, gender, birthday, mobile, email, address) VALUES(1, 张三, 男, 2000-01-01, 13838383838, zhangsanexample.com, 上海市某某路),(2, 李四, 男, 2000-02-02, 13939393939, lisiexample.com, 北京市某某路),(3, 王五, 男, 2000-03-03, 13636363636, wangwuexample.com, 广州市某某路),(4, 赵六, 女, 2000-04-04, 13737373737, zhaoliuexample.com, 深圳市某某路),(5, 钱七, 女, 2000-05-05, 13535353535, qianqiexample.com, 成都市某某路),(6, 孙八, 男, 2000-06-06, 13333333333, sunbaexample.com, 重庆市某某路),(7, 周九, 男, 2000-07-07, 13232323232, zhoujiuexample.com, 武汉市某某路),(8, 吴十, 女, 2000-08-08, 13131313131, wushiexample.com, 南京市某某路),(9, 郑十一, 男, 2000-09-09, 13030303030, zhengshiyiexample.com, 西安市某某路),(10, 王十二, 女, 2000-10-10, 12929292929, wangshierexample.com, 杭州市某某路);
外键
保证数据的完整性
CREATE TABLE borrowbook1 (sno INT,bookid INT,borrowdate DATE,returndate DATE,CONSTRAINT pk_borrowbook PRIMARY KEY (sno, bookid),CONSTRAINT fk_sno FOREIGN KEY (sno) REFERENCES student03(sno),CONSTRAINT fk_bookid FOREIGN KEY (bookid) REFERENCES book(bookid)
);create table book
(
bookid int,
bookname varchar(100),
author varchar(20),
press varchar(50),
price float(8,2),
constraint pk_bookid primary key(bookid)
)插入数据
根据您提供的信息我将为每个表提供两条插入语句的示例。对于borrowbook1表
sql
INSERT INTO borrowbook1 (sno, bookid, borrowdate, returndate) VALUES(1, 101, 2023-11-01, 2023-11-08),(2, 102, 2023-11-02, 2023-11-09);
上述示例插入了两条数据到borrowbook1表中。对于book表
sql
INSERT INTO book (bookid, bookname, author, press, price) VALUES(101, 书籍1, 作者1, 出版社1, 29.99),(102, 书籍2, 作者2, 出版社2, 39.99);
上述示例插入了两条数据到book表中。对于student03表
sql
INSERT INTO student03 (sno, sname, gender, birthday, mobile, email, address) VALUES(1, 张三, 男, 2000-01-01, 13838383838, zhangsanexample.com, 上海市某某路),(2, 李四, 男, 2000-02-02, 13939393939, lisiexample.com, 北京市某某路);
上述示例插入了两条数据到student03表中。请根据需要修改每条插入语句中的具体值。如果插入一个学号为空的值则报错学号11是没有数据的在student3 表格中
sno和bookid 在 borrowbook1 表中是属于外键所以插入之前会去student3 表格中去找下 sno 是不是有学号 11 没有则如下图一样报错
INSERT INTO borrowbook1 (sno, bookid, borrowdate, returndate) VALUES(11, 101, 2023-11-02, 2023-11-05)实战
create table student
(
sno int auto_increment comment 学号,
sname varchar(20) not null comment 姓名,
gender char(3) not null comment 性别,
birthday date comment 出生日期,
mobile varchar(20) comment 手机号,
email varchar(100) comment 邮箱地址,
address varchar(200) comment 家庭住址,
constraint pk_sno primary key(sno),
constraint uq_mobile unique(mobile),
constraint uq_email unique(email)
) auto_increment 95001;INSERT INTO student (sname, gender, birthday, mobile, email, address) VALUES (张三, 男, 1995-01-01, 13812345678, zhangsanexample.com, 北京市东城区);
INSERT INTO student (sname, gender, birthday, mobile, email, address) VALUES (李四, 女, 1996-02-02, 13987654321, lisiexample.com, 上海市浦东新区);
INSERT INTO student (sname, gender, birthday, mobile, email, address) VALUES (王五, 男, 1997-03-03, 13611112222, wangwuexample.com, 广州市天河区);CREATE TABLE book (bookid INT AUTO_INCREMENT COMMENT 图书编号,bookname VARCHAR(100) NOT NULL COMMENT 图书名称,author VARCHAR(20) NOT NULL COMMENT 作者,press VARCHAR(100) NOT NULL COMMENT 出版社,price FLOAT(8, 2) NOT NULL COMMENT 图书价格,CONSTRAINT pk_bookid PRIMARY KEY (bookid)
) AUTO_INCREMENT 112;INSERT INTO book (bookname, author, press, price) VALUES (书籍1, 作者1, 出版社1, 29.99);
INSERT INTO book (bookname, author, press, price) VALUES (书籍2, 作者2, 出版社2, 39.99);
INSERT INTO book (bookname, author, press, price) VALUES (书籍3, 作者3, 出版社3, 49.99);CREATE TABLE borrowbook
(borrowid INT AUTO_INCREMENT COMMENT 借书编号,sno INT COMMENT 学号,bookid INT COMMENT 图书编号,borrowdate DATETIME DEFAULT CURRENT_TIMESTAMP COMMENT 借书时间,returndate DATETIME DEFAULT NULL,CONSTRAINT pk_borrowbook PRIMARY KEY (borrowid),CONSTRAINT fk_sno FOREIGN KEY (sno) REFERENCES student(sno),CONSTRAINT fk_bookid FOREIGN KEY (bookid) REFERENCES book(bookid)
);-- 插入示例数据
INSERT INTO borrowbook (sno, bookid) VALUES (95001, 112);
INSERT INTO borrowbook (sno, bookid) VALUES (95002, 113);
INSERT INTO borrowbook (sno, bookid) VALUES (95003, 114);
