select * from dept,employee where exists(select did from employee where age>21);
create view view_sales as select first_half+latter_half from sales
select p1.* from employee p1 join employee p2 on p1.did =p2.did where p2.name="王红"；
select * from send where datediff(dd,sendtime,getdate())=0;
CREATE INDEX index_subject 一> ON content(subject(3)ASC);
select * from score group by 学号 having sum(分数)>180;
CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` VIEW `v_hpkcb` AS SELECT
hpkcb.kcid,
hpkcb.kcsl,
hpmcb.hpmc,
hpmcb.jldw
FROM
hpkcb
INNER JOIN
hpmcb
ON
hpkcb.kcid = hpmcb.Hpid
————————————————
