????????????
????1.???????????:
????create table demo1(
????id int primary key??
????name varchar(40)
????);
????2.?????id:
????insert into demo1(name) values('aaa');/*????????????????*/
????3.?????????id:
????insert into demo1(id??name) values(1??'aaa');
????/*????????????????*/
????insert into demo1(id??name) values(1??'aaa');
????4.????????????????(auto_increment):
????create table demo2(
????id int auto_increment primary key??
????name varchar(40)
????);
????5.???????(unique):
????create table demo3(
????id int auto_increment primary key??
????name varchar(40) unique /*unique:???*/
????);
????6.??????(not null):
????create table demo4(
????id int auto_increment primary key??
????name varchar(40) not null
????);
????7.??????????():
????create table department(
????id int auto_increment primary key??
????name varchar(30) not null
????);
????create table employee2(
????id int auto_increment primary key??
????name varchar(30) not null??
????salary  double??
????department_id int??
????/*??????*/
????constraint department_id_FK foreign key(department_id) references department(id)
????);
????6.??????(not null):
????create table demo4(
????id int auto_increment primary key??
????name varchar(40) not null
????);
????7.???????:
????alter table tablename drop primary key;