数据库 P3306
create database [if not exists] db_name [characterset gbk];
use database;//跳转数据库
show databases;
alert database db_name character set utf8;//修改
drop databases [ if not exists] dbname ;//最有用的
show create databses dbname;
表
create table [i n e] tbname(
id smallint unsigned primarykey auto_increment,
name varchar(10) not null,
);
not null非空 auto_increment自增 primary key unique key 唯一约束
default ‘ ‘
describe[desc] stu;
show tables;
show create table tbname;
alert table users1 add age tinyint unsigned not null default 10;
alert table tbname add colname coldef,…//添加多列
alert table tbname add password varchar(32) not null after username//在username后添加
alert table tbname add truename varchar(10) not null first//最前
alert table tbname drop password,drop age;//删除多列
int tinyint decimal(legth,dec) text char varchar //数据类型
增
insert into tbname(collist) values(val)
删
delete from tbname where name=xx;
更
update tbname set col=” where xx=xx;
查
select colname from tbname where …… order by colname asc默认|desc降序 limit 3,2
and并且 or或者 not
min max sum avg count()
