3 日期类型/字符类型/枚举类型/集合类型/约束条件

create table student(
    id int,
    name char(6),
    born_year year,
    birth_date date,
    class_time time,
    reg_time datetime    
);

insert into student values
(1,'eddie',now(),now(),now(),now());

字符类型

1 char: 定长

2 varchar: 变长

#宽度指的是字符的个数

create table t1(name char(5));

create table t2(name varchar(5));

insert into t1 values('李杰 ')；

insert into t2 values('李杰')；

select char_length(name) from t1;

select char_length(name) from t2;

枚举类型/集合类型

create table consumer(
    id int,
    name char(16),
    sex enum('male','female','other'),
    level enum('vip1','vip2','vip3'),
    hobbies set('play','music','read','run')
);



insert into consumer values
(1,'eddie','male','vip2','music,read');

约束条件not null 和 default

create table t15(
    id int(11) unsigned zerofill
);



create table t16(
    id int,
    name char(10),
    sex enum('male','female') not null default 'male'
);

insert into t16(id, name) values(1,'eddie');

unique key

create table department(
    id int unique,
    name char(10) unique
);


insert into department values
(1,'IT'),
(2,'SALE');

联合唯一

create table services(
    id int,
    ip char(15),
    port int,
    unique(id),
    unique(ip,port)
);


insert into services values
(1,'192.168.1.10',80),
(2,'192.168.1.10',81),
(3,'192.168.1.13',80);

primary key

约束： not null unique

存储引擎（innodb）: 对于innodb存储引擎来说，一张表内必须有一个主键

单列主键

create table t18(
    id int not null unique,
    name char(10)
);

复合主键

create table t19(
    ip char(10),
    port int,
    primary key(ip,port)
);

insert into t19 values
('1.1.1',80),
('1.1.1',81);

auto_increment 自增长

create table t20(
    id int primary key auto_increment,
    name char(16)
);

insert into t20(name) values
('eddie'),
('david'),
('wxx');

insert into t20(id,name)values
(7,'xxxx');


show variables like 'auto_inc%';

#步长  auto_increment_increment  默认为1
#起始偏移量 auto_increment_offset 默认为1

#设置步长 
set session auto_increment_increment=5;
set global auto_increment_increment=5

#设置起始偏移量
set global auto_increment_offset=3;
起始偏移量小于等于步长

清空表

delete from t20;     #auto_increment 没有删除  用delete 删除固定的id


truncate t20;  建议用这个清空表

3 日期类型/字符类型/枚举类型/集合类型/约束条件

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