Delete records with recursive foreign key constraints - mysql

Question

What is the best approach to delete records from a table which has a foreign key to another table and the other table has a foreign key to it?
For instance, I have the following tables. accounts has one or more networks and accounts must have a single default network.
CREATE TABLE IF NOT EXISTS accounts (
id INT NOT NULL,
networksId INT NOT NULL,
PRIMARY KEY (id),
INDEX fk_accounts_networks1_idx (networksId ASC),
CONSTRAINT fk_accounts_networks1
FOREIGN KEY (networksId)
REFERENCES networks (id)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
CREATE TABLE IF NOT EXISTS networks (
id INT NOT NULL AUTO_INCREMENT,
accountsId INT NOT NULL,
PRIMARY KEY (id),
INDEX fk_sites_accounts1_idx (accountsId ASC),
CONSTRAINT fk_sites_accounts1
FOREIGN KEY (accountsId)
REFERENCES accounts (id)
ON DELETE CASCADE
ON UPDATE NO ACTION)
ENGINE = InnoDB;
Even though I have a CASCADE DELETE on networks FK to accounts, I tried to explicitly delete networks in hopes of getting around the foreign key constraint, however, was not successful.
DELETE a, n FROM accounts a INNER JOIN networks n ON n.accountsId=a.id WHERE a.id=123;
Is my only solution something like the following?
SET FOREIGN_KEY_CHECKS=0;
DELETE FROM networks WHERE accountsId=123;
SET FOREIGN_KEY_CHECKS=1;
DELETE FROM accounts WHERE id=123;

Answer 1

You have a constraint interdependency between both tables. This is not a good design, because it tends to make DDL and DML operations more complicated than normally necessary.
Apart from temporarily disabling a foreign key, the only possible solution to perform a successful DELETE is to make one of the referencing fields nullable so you can break the relation by setting it to NULL before deleting. The ON DELETE CASCADE will take care of dropping the related record in the other table.
Make one the referencing fields nullable :
ALTER TABLE networks MODIFY accountsId INT NULL;
Delete :
UPDATE network SET accountsId = NULL WHERE id = ?;
DELETE FROM network WHERE id = ?;
-- the corresponding record in table accounts gets automatically deleted.