今天具体学了下 MySQL的操作；
mysql 对大小写不敏感 所以大写只是为了区分关键字与 数据

create database databasename;
create table tablename;
describe tablename;
select * from tablename;
select columnname1,..., from tablename;
alter  table tablename add constriant primary key column1;
insert into tablename values(.......,.....,.....);
select ................where ....like '  '// '_'代表一个字符 '%'代表多个字符
order by  desc 降序    /asc升序
in       not in
and     or