1 增加 (Create)

(1) 完全插入

insert classes values(0, "江湖菜鸟");

insert students values(0, "余沧海", 20, "男", 0, "1990-01-01");

insert students(name, gender) values("黄蓉", "女");

insert students(name, gender) values("摘星子", "男"), ("费彬", "男");

delete from students where name="黄蓉";

用一个字段来表示,这条信息是否已经不能再使用了
给表添加一个is_delete字段, bit类型
alter table students add is_delete bit default 0;
update students set is_delete=1 where id=X;

update students set age=18,gender=2 where id=3;

select * from classes;

select * from students where gender=2;

select name, gender from students;

select name as 姓名, gender as 性别 from students;

select distinct gender from students;