MySQL 笔记

mysql
create database mydatabase;
use database;
show database;
drop database;
select database();
select version();
desc tablename;
net start mysql
net stop mysql
DQL select
DML insert updata delete
DDL create
TCL commit rollback
DCL grant revoke
source c://data.sql
ctrl+c
show create table orz;
select name '姓名' from driver;
<> !=
between small and big
is null
ifnull(name,2)
select 8 from driver where name like '_A%'
order by money asc/desc 升降
order by 1 asc/desc 升降
lower（name）
upper（name）
lenth(name)
substr(name,2,3)
round (123.456,0)
rand()
trim(' wqeqw ')
str_to_date('日期字符串'，‘日期格式’)
%Y %m %d %H %i %s
select time from timetable where data=str_to_date('12-7-1980','%m-%d-%Y')
date_format('日期格式类型数据'，‘日期格式’)
sum()
avg()
max()
count()
count(*)
min()
select distinct name from tablename;
select distinct name,age from tablename;
create table emp1 as select * from emp;
insert into emp select * from emp1;
alter table t_student add name varchar(10);
alter table t_student motify name varchar(20);
alter table t_student drop name
not null
unique 不能重复，但可为null unique(name,age)联合表级约束，联合唯一
primary key
foreign key
constaint user_name_unique unique(name)给约束起名字
外键字段可以为空，被引用表字段必须要有唯一性
constraint student_class_fk foreign key(classno) references class(cno)
show engeins;
start transaction;
commit;
rollback;
set autocommit=off/on;
set session autocommit=off/on