mysqlデータベースの簡単なsql文

#      ，        

#cmd   mysql   (    mysql，  5.5，              )
net start mysql

#cmd   mysql  
net stop mysql

#    mysql    (-h     -P     -u     -p   )
mysql -h localhost -P 3306 -u root -p

#    mysql      
mysql -u root -p

#       
show databases;

#        studyit 
create database studyit;

#     
drop database studyit;

#        studyit          
create database if not exists studyit;

#               studyit
show create database studyit;

#      studyit
use studyit;

#          
select database();

#          
show tables;

#      class  
create table class(
    id int(4) null auto_increment primary key,
    class_name varchar(10) unique not null,
    stu_num int(4)
);

#       stu 
drop table stu;

#      class      
show create table class;

#           
desc class;

# class      
insert into class values(null,'class01',100);
insert into class values(null,'class02',130);

#       
select * from class;

# class           
insert into class (class_name) values ('class03');
insert into class (class_name,stu_num) values ('class04',200);

#  id 4     
delete from class where id=4;

#         (  where  ，      )
update class set stu_num=100;

#               
update class set stu_num=200 where class_name='class03';

# delete  user1       
#    ，    ，      ，     
detele from user1;

# delete  user2       
delete from user2 where id=3;

#   user ，    ，    ，     
truncate user;(       truncate table user;)

#  class  id=1     class_name    
select class_name from class where id = 1;

#  class  class_name='class03'     id stu_num    
select id,stu_num from class where class_name='class03';

#   class  stu_num   (    )
select distinct(stu_num) from class;

#  class  stu_num=100     id class_name
select id,class_name from class where stu_num = 100;

#  class  id>=2   
select * from class where id >= 2;

#  class    class_name class01 class02    id;
select id from class where class_name in('class01','class02');

#  class  id 2 3     
select * from class where id between 2 and 3;

#    class_name c   stu_num     
select stu_num from class where class_name like 'c%';

#    class_name  01     
select * from class where class_name like '%01%';

#    class_name       a,       3 id     
#  :a        
select * from class where class_name like '__a%3';