SQL LESSON 1

数据库
表---程序
通过mysql dbms来编辑数据库

查询 select

插入 insert

删除 delete

更新 update

create database abcde
create table st(name char(10),age int(2),no char(10));

一行数据叫元组

select * from st;
//2个记录，都是3列的

select name from st 
//显示的是
abc
def

select * from st where age >10;
//返回一条记录，三列

select * from st where age >10 or no like "%2012%"

delete * from st; //删除所有
delete from st where age>20;

update st set age=age+1 where age<14;
insert into st values('DEF',20,'0123');
insert into st(name,age) values('A*',10);

drop table st;//关了数据库
alter table

实体 entity
属性1
属性2