Multi table deletion MySQL through PHP - php

Question

I am making a simple database to use as a mock example for an E-Commerce website. One things that I am required to do it delete records from the database using PHP. I can delete a user name or a order or etc.. But when I try to do them all at once I am screwing something up. What I want to happen is delete all the information about a user. Example : User info, Shipping Info, Billing Info, Credit Card Info, and anything else to do with the specific user. My tables are as followed.
mysql> SHOW columns FROM shirt_billing_addresses;
+----------------------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------------------------+--------------+------+-----+---------+----------------+
| shirt_billing_addresses_id | mediumint(9) | NO | PRI | NULL | auto_increment |
| house | mediumint(9) | NO | | NULL | |
| street | varchar(100) | NO | | NULL | |
| city | varchar(100) | NO | | NULL | |
| state | char(2) | NO | | NULL | |
| zip | char(5) | NO | | NULL | |
+----------------------------+--------------+------+-----+---------+----------------+
6 rows in set (0.01 sec)
mysql> SHOW columns FROM shirt_credit_cards;
+-----------------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------------------+--------------+------+-----+---------+----------------+
| shirt_credit_cards_id | mediumint(9) | NO | PRI | NULL | auto_increment |
| shirt_users_id | mediumint(9) | NO | MUL | NULL | |
| type | varchar(30) | NO | | NULL | |
| no | char(16) | NO | | NULL | |
| security_code | char(3) | NO | | NULL | |
+-----------------------+--------------+------+-----+---------+----------------+
5 rows in set (0.04 sec)
mysql> SHOW columns FROM shirt_orders;
+-----------------------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------------------------+--------------+------+-----+---------+----------------+
| shirt_orders_id | int(11) | NO | PRI | NULL | auto_increment
| order_total | double(6,2) | NO | | NULL | |
| payment_date | datetime | NO | | NULL | |
| shirt_credit_cards_id | mediumint(9) | NO | MUL | NULL | |
| shirt_shipping_addresses_id | mediumint(9) | NO | MUL | NULL
| shirt_billing_addresses_id | mediumint(9) | NO | MUL | NULL |
| shirt_shipping_methods_id | tinyint(4) | NO | MUL | NULL |
+-----------------------------+--------------+------+-----+---------+----------------+
7 rows in set (0.02 sec)
mysql> SHOW columns FROM shirt_shipping_addresses;
+-----------------------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------------------------+--------------+------+-----+---------+----------------+
| shirt_shipping_addresses_id | mediumint(9) | NO | PRI | NULL | auto_increment
| house | mediumint(9) | NO | | NULL | |
| street | varchar(100) | NO | | NULL | |
| city | varchar(100) | NO | | NULL | |
| state | char(2) | NO | | NULL | |
| zip | char(5) | NO | | NULL | |
+-----------------------------+--------------+------+-----+---------+----------------+
6 rows in set (0.03 sec)
mysql> SHOW columns FROM shirt_users;
+----------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------------+--------------+------+-----+---------+----------------+
| shirt_users_id | mediumint(9) | NO | PRI | NULL | auto_increment |
| first_name | varchar(30) | NO | | NULL | |
| last_name | varchar(30) | NO | | NULL | |
| email | varchar(30) | NO | | NULL | |
| user_id | varchar(30) | NO | | NULL | |
| password | char(40) | NO | | NULL | |
+----------------+--------------+------+-----+---------+----------------+
6 rows in set (0.03 sec)
mysql> SHOW columns FROM shirt_users_types;
+----------------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------------------+--------------+------+-----+---------+----------------+
| shirt_users_types_id | int(11) | NO | PRI | NULL | auto_increment |
| shirt_users_id | mediumint(9) | NO | MUL | NULL | |
| shirt_types_id | smallint(6) | NO | MUL | NULL | |
| shirt_orders_id | int(11) | NO | MUL | NULL | |
| type_quantity | smallint(6) | NO | | NULL | |
| type_total | double(6,2) | NO | | NULL | |
+----------------------+--------------+------+-----+---------+----------------+
6 rows in set (0.03 sec)
The PHP code I have is as follows:
#mysqli_query($link, "SET AUTOCOMMIT=0");
$select_sui = "SELECT
shirt_users.shirt_users_id,
shirt_users_types.shirt_users_types_id,
shirt_orders.shirt_orders_id,
shirt_shipping_addresses.shirt_shipping_addresses_id,
shirt_billing_addresses.shirt_billing_addresses_id,
shirt_credit_cards.shirt_credit_cards_id
from
shirt_users,
shirt_users_types,
shirt_orders,
shirt_shipping_addresses,
shirt_billing_addresses,
shirt_credit_cards
where
shirt_users.shirt_users_id = shirt_users_types.shirt_users_id and
shirt_users_types.shirt_orders_id = shirt_orders.shirt_orders_id and
shirt_orders.shirt_shipping_addresses_id = shirt_shipping_addresses.shirt_shipping_addresses_id and
shirt_orders.shirt_billing_addresses_id = shirt_billing_addresses.shirt_billing_addresses_id and
shirt_orders.shirt_credit_cards_id = shirt_credit_cards.shirt_credit_cards_id and
shirt_users.shirt_users_id = $shirt_users_id";
The only problem is that this query will return an empty set unless all the tables have the correct information in it. This is a problem because if a user has not ordered any items yet but I want to delete them from the database, It will not allow me. Any help on this matter would be greatly appreciated.

Answer 1

You have to use LEFT JOIN to link your tables (MySQL doc).
SELECT [...]
FROM shirt_users
LEFT JOIN shirt_users_types ON shirt_users.shirt_users_id = shirt_users_types.shirt_users_id
LEFT JOIN shirt_orders ON shirt_users_types.shirt_orders_id = shirt_orders.shirt_orders_id
LEFT JOIN shirt_shipping_addresses ON shirt_orders.shirt_shipping_addresses_id = shirt_shipping_addresses.shirt_shipping_addresses_id
LEFT JOIN shirt_billing_addresses ON shirt_orders.shirt_billing_addresses_id = shirt_billing_addresses.shirt_billing_addresses_id
LEFT JOIN shirt_credit_cards ON shirt_orders.shirt_credit_cards_id = shirt_credit_cards.shirt_credit_cards_id
WHERE
shirt_users.shirt_users_id = $shirt_users_id
With this you'll be able to load shirt_users even if there is no linked record in other tables.
EDIT for Delete records
If you want to delete in all your tables in only one request, you must use as syntax which is fairly the same as your first try (by replacing the SELECT statement by DELETE). ANd you will get the same problem (it will only delete records which have a linked record in each table and not null).
Method 1 :
NB : Your DB must support foreign keys (for example, MyISAM doesn't support it but InnoDB does).
You can use this method, if you always need in your app to delete all linked records.
The most beautiful way to achieve this is to add a ON DELETE CASCADE constraint on your relations :
-- Drop the old constraint ("fk_test" must be replace by your constraint name)
ALTER TABLE shirt_users_types DROP FOREIGN KEY `fk_test`;
-- Create the new with ON DELETE
ALTER TABLE shirt_users_types
ADD CONSTRAINT `fk_test`
FOREIGN KEY (`shirt_users_id` )
REFERENCES `shirt_users` (`shirt_users_id` )
ON DELETE CASCADE;
When you will delete a shirt_users entry, all linked records in shirt_users_types.
In a few words, with ON DELETE CASCADE, each time you will delete a parent element (the One side of the relation), all the children (the Many side of the relation or the table wich contains the column <related_record>_id) will be automatically deleted too.
Method 2 :
If your relation can be nullable (for example if shirt_users_types.shirt_orders_id can be null) or if your DB schema not permits to delete all needed records with ON DELETE CASCADE.
You can delete your records with several DELETE using relations to shirt_users in order to retrieve records in each linked table. (For correct syntax of DELETE with relations see MySQL docs).
In your code your unique identifier is $shirt_users_id, so you have to start by deleting in the tables which are not directly linked to shirt_users and by reaching back your relations to finish by the table shirt_users.
If you don't delete records in the correct order, you will not be able to delete all you need.
For example, with schema described in your question, if you delete records in shirt_orders before shirt_shipping_addresses, you will no longer can retrieve shipping addresses with $shirt_users_id because shirt_shipping_addresses is linked to shirt_users due to its relation with shirt_orders.
So the correct order for your current schema is (there is no need to have an order for table on the same line the list above) :
shirt_shipping_addresses / shirt_billing_addresses
shirt_orders / shirt_credit_cards / shirt_users_types
shirt_users
You can have a contraint fails error due to foreign keys. In this case you can make your delete in a TRANSACTION (it's a best practice) or disable foreign key checks for your queries.
SET foreign_key_checks = 0;