Eche un vistazo a este hilo similar donde escribí un sp para realizar la tarea
Unir dos tablas (con una relación 1-M) donde la segunda tabla debe 'aplanarse' en una fila
editar. Respuesta actualizada
create table `pivot` (
`id` int(11) not null auto_increment,
`categoryid` int(11) default null,
`processdate` date default null,
`percentchange` int(11) default null,
primary key (`id`)
) engine=myisam auto_increment=9 default charset=latin1;
/*Data for the table `pivot` */
insert into `pivot`(`id`,`categoryid`,`processdate`,`percentchange`) values (1,4,'2011-05-10',1);
insert into `pivot`(`id`,`categoryid`,`processdate`,`percentchange`) values (2,4,'2011-05-11',22);
insert into `pivot`(`id`,`categoryid`,`processdate`,`percentchange`) values (3,4,'2011-05-12',3);
insert into `pivot`(`id`,`categoryid`,`processdate`,`percentchange`) values (4,7,'2011-05-10',4);
insert into `pivot`(`id`,`categoryid`,`processdate`,`percentchange`) values (5,7,'2011-05-11',5);
insert into `pivot`(`id`,`categoryid`,`processdate`,`percentchange`) values (6,12,'2011-05-10',6);
insert into `pivot`(`id`,`categoryid`,`processdate`,`percentchange`) values (7,12,'2011-05-12',7);
insert into `pivot`(`id`,`categoryid`,`processdate`,`percentchange`) values (8,4,'2011-05-13',12);
delimiter //
drop procedure if exists dynamic_view2//
create procedure dynamic_view2(in sdate date,in edate date)
begin
declare finish int default 0;
declare cdate date;
declare str varchar(10000) default "select categoryid,";
declare curs cursor for select processdate from pivot where processdate between sdate and edate group by processdate;
declare continue handler for not found set finish = 1;
open curs;
my_loop:loop
fetch curs into cdate;
if finish = 1 then
leave my_loop;
end if;
set str = concat(str, "max(case when processdate = '",cdate,"' then percentchange else null end) as `",cdate,"`,");
end loop;
close curs;
set str = substr(str,1,char_length(str)-1);
set @str = concat(str," from pivot
group by categoryid");
prepare stmt from @str;
execute stmt;
deallocate prepare stmt;
end;//
delimiter ;
mysql> call dynamic_view2('2011-05-10','2011-05-13');
+------------+------------+------------+------------+------------+
| categoryid | 2011-05-10 | 2011-05-11 | 2011-05-12 | 2011-05-13 |
+------------+------------+------------+------------+------------+
| 4 | 1 | 22 | 3 | 12 |
| 7 | 4 | 5 | NULL | NULL |
| 12 | 6 | NULL | 7 | NULL |
+------------+------------+------------+------------+------------+
3 rows in set (0.00 sec)
