Some other options for dealing with foreign key relationships that may be workable for your use-case are BEFORE DELETE triggers, and/or ON DELETE rules on the foreign key constraints.) On the other hand, if we don't want to remove 'Spot', because the 'Jill'/'Spot' row in own also references 'Spot', we might be able to do something very similar.

We can accomplish that using two references to the own table one to get the relationship between 'Jack' and his owned pet, and another to get all of the own rows that reference 'Spot'.

If we do really want to delete 'Spot', we would also need to remove that other row from own too, the one that relates 'Spot' and 'Jill'.

So, the question is, do we really want to delete 'Spot' in this case? There's another row in own that references 'Spot', so we wouldn't be able to remove 'Spot', without also removing 'Spot''s relationship to 'Jill'. But in this scenario, 'Spot' is also related to 'Jill'. If we were to delete 'Jack', we could remove the associated row in 'own' (the relationship between 'Jack' and 'Spot'. The data model suggests that a pet may be related to more than one people. (For example, if there's another table with a foreign key that references pet.petid, and we delete the 'parent' row from pet, that may leave a rows in the 'child' table that reference a non-existent key.) So, this approach is less than ideal, because of the potential for introducing inconsistent data. SET foreign_key_checks = 1 īut this disables ALL foreign key checks in the session, not just the foreign keys defined on the tables referenced in the DELETE. Then the DELETE statement, and then re-enable the foreign key checks. But with InnoDB, if there are foreign key constraints defined, this can be a problem Unfortunately, InnoDB doesn't (yet?) support deferrable constraints, so the closest workaround to this is to temporarily disable foreign key checks. This isn't a problem with MyISAM, since it doesn't enforce foreign keys. The rows may be deleted in an order that causes foreign key constraints to be violated. One option is to use a multitable DELETE statement, to delete rows from all three tables, for example: DELETE o.*īut. MySQL Trigger: Delete From Table AFTER DELETE It will automatically delete entries from own table with peopleid = 3 and the corresponding petid from Pet table. CREATE TRIGGER pet_delete AFTER DELETE on ownĪfter defining the cascade rule and trigger, if you execute: DELETE FROM People WHERE peopleid = 3 Since pet table has no foreign key to people table, you need to define a trigger to auto delete pet entries when people entries are deleted. In your case, if you delete a person using peopleid, it will automatically remove the references from Own table. Using this, you can automatically remove all the table references, if you delete a primary key row. I think what you need is ON DELETE CASCADE. IF EXISTS: DROP USER bob ERROR 1396 ( HY000 ): Operation DROP USER failed for 'bob' '%' DROP USER IF EXISTS bob Query OK, 0 rows affected, 1 warning ( 0. Examples DROP USER bob DROP USER foo2 localhost, foo2 '127.%' If the IF EXISTS clause is used, MariaDB will return a note instead of an error if the user does not exist. Only one error is produced for all users which have notīeen dropped: ERROR 1396 (HY000): Operation DROP USER failed for CREATE or DROP operations, for both users and roles, produce the If an error occurs, DROP USER will still drop the accounts that do If any of the specified user accounts do not exist, ERROR 1396 (HY000) Note that, if you specify an account that is currently connected, it will notīe deleted until the connection is closed. For additional information about specifying account names, see Only the user name part of the account name, a host name part of '%' is Or the DELETE privilege for the mysql database.Įach account is named using the same format as for the CREATE USER You must have the global CREATE USER privilege Privilege rows for the account from all grant tables. The DROP USER statement removes one or more MariaDB accounts.

Mysql delete user force