创建数据库+删除数据库+创建表等

1.创建数据库
create database 数据库名称;
2.删除数据库
drop database test2;

3.创建表

create table ceshi
(
ids int auto_increment primary key,
uid varchar(20),
name varchar(20),
class varchar(20),
foreign key (class) references class(code) 
);
create table class
(
code varchar(20) primary key,
name varchar(20) not null
);

**自增长 auto_increment
**主键 primary key
**外键 foreign key (列名) references 主表名(列名)
**非空 not null

4.删除表
drop table ceshi;

注意：
1.类型包含长度的在类型后面加括号，括号里面写长度
2.上一列写完加逗号
3.最后一列不要写逗号
4.在每一条SQL语句写完之后要加分号
5.如果有外键关系，先创建主表

create table class
(
    code varchar(20) primary key,
    name varchar(20)
);
create table student
(
    code varchar(20) primary key,
    name varchar(20),
    sex bit,
    age int,
    class varchar(20),
    foreign key (class) references class(code)
);

create table teacher 
(
    code varchar(20) primary key,
    name varchar(20)
);
create table chengji
(    
    ids int auto_increment primary key,
    scode varchar(20),
    kcode varchar(20),
    degree float,
    foreign key (scode) references student(code),
    foreign key (kcode) references kecheng(code)
);

create table tkecheng
(
    ids int auto_increment primary key,
    tcode varchar(20),
    kcode varchar(20),
    foreign key (kcode) references kecheng(code),
    foreign key (tcode) references teacher(code)
);