Question

I have created a stored procedure to delete data from multiple tables. my work flow as follows

I’m using mysql 5.0 and running on linux

table dependencies as follows

table C depending on table B
table B depending on table A

I want to delete a record in table A and delete all the related records in tables B and C

1 – delete all the data from detail tables (C) (with stored procedure sp_delete_from_C)

2 – delete related data immediate child table (B) (with stored procedure sp_delete_from_B)

3 – delete master table (A) (with stored procedure sp_delete_from_A)

I have wrote the following procedure

CREATE PROCEDURE sp_A_rollback(IN aId INT UNSIGNED)
READS SQL DATA
BEGIN
DECLARE b_id INT DEFAULT 0;

DECLARE cur_1 CURSOR  FOR SELECT id FROM b where a_id=aId;

OPEN cur_1;
read_loop: LOOP
  FETCH cur_1 INTO a_id;
  CALL sp_delete_from_C(b_id);
END LOOP;
CLOSE cur_1;

CALL sp_delete_from_B(aId);
CALL sp_delete_from_A(aId);


END //

My question is,

If i run these procedures individually it works

but if u run sp_A_rollback it execute only ‘sp_delete_from_C’

I dont have any idea why its not calling the other 2 sps. I’m a newbee to mysql stored procedures. please can someone help me

thanks in advance

sameera

Answer 1

I have no idea why you’re using cursors – all you need is something like the following:

drop procedure if exists cascade_delete_tableA;
delimiter #

create procedure cascade_delete_tableA
(
in p_id int unsigned
)
begin

delete from tableC where a_id = p_id;
delete from tableB where a_id = p_id;
delete from tableA where id = p_id;

end#

delimiter ;

call the stored procedure from your application code wrapped up in a transaction.

EDIT

You’ll need to use a join to delete rows from your tableC. Here’s a more comprehensive example for you to study http://pastie.org/1435521. Also, your cursor loop isnt fetching into the correct variable which is why it’s not working in it’s current form. I would still recommend you examine the following…

-- TABLES

drop table if exists customers;
create table customers
(
cust_id smallint unsigned not null auto_increment primary key,
name varchar(255) not null
)
engine=innodb;

drop table if exists orders;
create table orders
(
order_id int unsigned not null auto_increment primary key,
cust_id smallint unsigned not null
)
engine=innodb;

drop table if exists order_items;
create table order_items
(
order_id int unsigned not null,
prod_id smallint unsigned not null,
primary key (order_id, prod_id)
)
engine=innodb;

-- STORED PROCS

drop procedure if exists cascade_delete_customer;
delimiter #

create procedure cascade_delete_customer
(
in p_cust_id smallint unsigned
)
begin

declare rows int unsigned default 0;

-- delete order items

delete oi from order_items oi 
 inner join orders o on o.order_id = oi.order_id and o.cust_id = p_cust_id;

set rows = row_count();

-- delete orders

delete from orders where cust_id = p_cust_id;

set rows = rows + row_count();

-- delete customer

delete from customers where cust_id = p_cust_id;

select rows + row_count() as rows;

end#

delimiter ;

-- TEST DATA

insert into customers (name) values ('c1'),('c2'),('c3'),('c4');

insert into orders (cust_id) values (1),(2),(3),(1),(1),(3),(2),(4);

insert into order_items (order_id, prod_id) values 
(1,1),(1,2),(1,3),
(2,5),
(3,2),(3,5),(3,8),
(4,1),(4,4),
(5,2),(5,7),
(6,4),(6,8),(6,9),
(7,5),
(8,3),(8,4),(8,5),(8,6);

-- TESTING

/*

select * from customers where cust_id = 1;

select * from orders where cust_id = 1;

select * from order_items oi 
 inner join orders o on oi.order_id = o.order_id and o.cust_id = 1;

call cascade_delete_customer(1);

*/