sudo apt-get install mysql-server
pa aux | grep mysql
sudo service mysql start
sudo service mysql status
./start_navicat
CRUD
create database db1;
create database db2 charset=utf8;
create database db3 character set utf8;
show create database db2;
alter database db1 charset=utf8;
show databases;
use db3;
 
select database();
drop database db2;
use db3;
show tables;
create table mv(id int, name char(20), yr year);
show create table mv;
alter table mv add  dct_name char(20);
alter table mv drop dct_name;

alter table mv modify name varchar(20);
alter table mv change id id_num smallint;

select * from mv;
insert into 
 
mv (id, name) values(1,"Fast and Furious");
insert into mv values(2,"The Zootopia",2018),(3,"The Gifts",2019);
update mv set yr='2018';
truncate mv;
delete from mv;
delete from mv where yr=2017;
create table t_pk(id int primary key, name char(10));
create table t_atp(id int atuo_increment primary key, name char
 
(10));
create table t_un(id int unique, name char(10));
create table t_nn(id int, name varchar(10) not null);
create table t_dft(id int, name varchar(10) default "WW");

create table t_f(id int primary key, name char(10));
create table t_s(id int primary ket auto_increment, name char(10), fid int, foreign key(fid) references t_f(id));
drop table t_s;
drop table t_f;

create table t_chk(id int, age int check(age > 0 and age < 150), gender char(10) check('boy' or 'girl'));

alter table t_pk add constraint PK_id primary key(id);
alter table t_pk drop primary key;
alter table t_fk add constraint FK_id foreign key(id) references t_pk;
desc table t_fk;
alter table t_fk drop foreign key FK_id

mysqldump -uroot -p OriginS > bakp.sql
mysqldump -uroot -p OriginS t_s1, t_s2 > s1s2.sql
create database OSdb;
exit;
mysql -uroot -p OSdb < bakp.sql

select * from t_s1;
select c_id, c_name, c_addr from t_s1;
select c_id as 學號, c_name as 姓名,c_addr 地址 from t_s1;
select distinct c_addr from t_s1;
select * from t_s1 where c_age < 18;
select * from t_s1 where c_age = 23 and c_gender = 'girl';
select * from t_s1 where c_name like ''D";
select * from t_ s1 where c_id in range(5);×
select * from t_s1 where c_id in (1,3,8,9)
select * from t_s1 where c_age is not null;
select * from goods order by c_price asc;
select * from goods order by c_time desc;
select * from goods order by c_price asc, c_time desc;
select * from t_s1 limit 3;
select * from t_s1 limit 2, 10;

select c_gender from t_s1 group by c_gender;
select c_gender, c_addr from t_s1 group by c_gender, c_addr;
select c_gender ,group_concat(name) from t_s1 group by c_gender;
select gender, max(age), min(age), avg(age), sum(age), count(age) from t_s1 group by gender;
select gender, group_concat(name) from t_s1 group by gender having gender ='girl';
select gender, group_concat(name) from t_s1 where age <25 group by gender having gender = "girl";
select gender from t_s1 group by gender with rollup

select t_s.name, t_c.name from t_s, t_c where t_s.c_id = t_c.id;
select s.name 學生姓名, c.name 班級名稱 from t_s s, t_c c where s.c_id = c.id;
select s.name 學生姓名, c.name 班級名稱 from t_s as s inner join t_c c on s.c_id = c.id;
select s.name 學生姓名, c.name 班級名稱 from t_s s left join t_c c on s.c_id = c.id;
select s.name 學生姓名, c.name 班級名稱 from t_c c right join t_s s on s.c_id = c.id;

select * from t_s1 where age > (select avg(age) from t_s1);
select * from t_c where id in (select c_id from t_s1);
select * from t_s1 where (age, class_id) = (select max(age), min(class_id) from t_s1);
create table areas(id int primary key, atitle varchar(20), pid(int));
source ./areas.sql;
select count(*) from areas where pid is null;
select c.* from areas as c inner join areas p on c.pid = p.id where p.atitle ='湖南省'