数据库和数据表的创建和修改

create database if not exist zoo default character set gbk ;

alter database school character set utf8mb4;

use zoo;

show create database zoo;

drop database zoo;
create database db_system;

mysql> create table salary(
-> id int primary key auto_increment comment ‘id’,
-> userId int not null comment ‘用户id’,
-> baseSalary decimal(8,2) not null comment ‘基本工资’,
-> month int not null comment ‘月份’,
-> allowances decimal(6,2) not null DEFAULT(0) comment ‘补贴’);

alter table salary add image blob(255);
alter table salary modify job char(60)
alter table salary drop gender;
alter table salary rename to usersalary;
alter database db_system character set utf8mb4;
alter table user change name username char(20);