mysql> delimiter //
mysql> create procedure simpleproc (out param1 int)
-> begin
-> select count(*) into param1 from t;
-> end
-> //
query ok, 0 rows affected (0.00 sec)
mysql> delimiter ;
mysql> call simpleproc(@a);
query ok, 0 rows affected (0.00 sec)
mysql> select @a;
+------+
| @a |
+------+
| 3 |
+------+
1 row in set (0.00 sec)