一点实例明白mysql数据库存储过程

create procedure p1()
begin
select  * from t_news;

end $         //mysql存储过程 简单实例

create procedure p2(n int)    #含参
begin
select  * from t_category where cid > n;
end $      

create procedure p3(n int, j char(1))    #含参
begin  
if j='h'  then       #与其他语言不同 必须加then 注意符号= 不是==
 select  * from t_category where cid > n;
else
select  * from t_category where cid <n;   
end if;
end $    

create procedure p4(n smallint)    #含参
begin  
declare  i int;
declare s int;
set s = 0;
set i = 1;
while i<=n do
set s =s+i;
set i=i+1;
end while;
select s;
end $