New to sp, ERROR 1172 (42000): Result consisted of more than one row

[Alicia]

Hello,

I am new to stored procedures and I am trying to do a checking of my db data. But I get an error:

Existing tables:

mysql> describe pet;//
+---------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| name | varchar(20) | YES | | NULL | |
| owner | varchar(20) | YES | | NULL | |
| species | varchar(20) | YES | | NULL | |
| sex | char(1) | YES | | NULL | |
| birth | date | YES | | NULL | |
| death | date | YES | | NULL | |
+---------+-------------+------+-----+---------+-------+
6 rows in set (0.02 sec)

mysql> describe event;//
+--------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+--------------+------+-----+---------+-------+
| name | varchar(20) | YES | | NULL | |
| date | date | YES | | NULL | |
| type | varchar(15) | YES | | NULL | |
| remark | varchar(255) | YES | | NULL | |
| owner | varchar(20) | YES | | NULL | |
+--------+--------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

Stored procedure:

delimiter //
create procedure test.check_owner
(out name_id varchar(10), out species_id varchar(10))
language sql
not deterministic
sql security invoker
comment 'a procedure to check owner between event and pet tables'
BEGIN
declare comp varchar(15);
declare name_id2 varchar(10);
declare species_id2 varchar(10);
SELECT pet.owner<>event.owner,event.name,pet.species INTO comp,name_id2,species_id2 FROM event,pet WHERE pet.name=event.name;
IF comp=1 THEN
SET name_id=name_id2;
SET species_id=species_id2;
END IF;
END;//

I have tried with CASE too, instead of IF-THEN-ENDIF:

CASE comp
WHEN 1 THEN SET name_id=name_id2;
SET species_id=species_id2;
END CASE;
END;//

When I call it, I get this error:

mysql> CALL test.check_owner (@name_id,@species_id);//
ERROR 1172 (42000): Result consisted of more than one row

I want to obtain all rows that owner is different in both tables for the same record in both tables. I want to have the name and the specie of that different rows.

Thanks for your help,
Alicia