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SQL语句

1.创建数据库

create database test2;

2.删除数据库

drop database test2;

3.创建表

create table class
(
  code varchar(20) primary key,
  name varchar(20) not null
);

create table ceshi

(

  ids int auto_increment primary key,
  uid varchar(20),
  name varchar(20),
  class varchar(20),
  foreign key (class) references class(code)
);

**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

 

创建表(例子):
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 kecheng
(
  code varchar(20) primary key,
  name varchar(20)
);
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)
);

SQL语句