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Dec 30, 2023 · In SQL, CASCADE is used to update or remove an entry from both the parent and child tables at the same time. The ON DELETE or ON UPDATE query uses the phrase CASCADE as a conjunction. If a user tries to delete a statement that will affect the rows in the foreign key table, then those rows will be deleted when the primary key record is deleted.
MySQL ON DELETE CASCADE. ON DELETE CASCADE clause in MySQL is used to automatically remove the matching records from the child table when we delete the rows from the parent table. It is a kind of referential action related to the foreign key.
Feb 8, 2021 · ON DELETE CASCADE constraint is used in MySQL to delete the rows from the child table automatically, when the rows from the parent table are deleted. For example when a student registers in an online learning platform, then all the details of the student are recorded with their unique number/id.
May 17, 2022 · CASCADE in SQL is used to simultaneously delete or update an entry from both the child and parent table. The keyword CASCADE is used as a conjunction while writing the query of ON DELETE or ON UPDATE.
Jun 20, 2013 · When you delete a row from the "parent" table--from "that_table"--you remove a valid value from the possible values for the "child" table. To maintain data integrity, you have to do something to the "child" table. Cascading deletes is one thing you can do. Chapter and verse, from PostgreSQL docs.
The canonical example for Cascade Update is when you have a mutable foreign key, like a username that can be changed. You should not use Cascade Update with keys that are Identity/autoincrement columns. Cascade Update is best used in conjunction with a unique constraint. When To Use Cascading
Jul 3, 2019 · In this article, we will review on DELETE CASCADE AND UPDATE CASCADE rules in SQL Server foreign key with different examples. DELETE CASCADE : When we create a foreign key using this option, it deletes the referencing rows in the child table when the referenced row is deleted in the parent table which has a primary key.
In PostgreSQL, the DELETE CASCADE is a referential action that allows you to automatically delete related rows in child tables when a parent row is deleted from the parent table. This feature helps you maintain referential integrity in the database by ensuring that dependent rows are removed when their corresponding rows are deleted.
Aug 16, 2023 · What is On Delete Cascade in SQL? The ON DELETE CASCADE is an option when defining a foreign key in SQL. It indicates that related rows should be deleted in the child table when rows are deleted in the parent table.
However, MySQL provides a more effective way called ON DELETE CASCADE referential action for a foreign key that allows you to delete data from child tables automatically when you delete the data from the parent table.
