1.create index index_subject on db_test.content(subject(3) ASC);
2.select * from db_test.content into outfile C:/backupcontent.txt;
3.net start mysql
mysql -u root
net stop mysql
mysql -remove
4.郑州
select * from student_web where s_tuition<(select avg(s_tuition) from student)
5.
select * from send where DATEDIFF(day,endtime,GETDATE())=0;
6.create view sales_view as select first_half+latter_half
from sales;
7.select * from dept exists(select did from employee where age>21);
select p1.* from employee p1 hoin employee p2 on p1.did=p2.did where p2.name='王红';
