MySQL ON DELETE CASCADE

Question

I have been working on MySQL for the past few months. Kindly apologize if my question is silly.

We have Foreign key Checks,

Enable - SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS,FOREIGN_KEY_CHECKS=1;

Disable - SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS,FOREIGN_KEY_CHECKS=0;

Similarly,

Do we have any Query to Enable and Disable ON DELETE CASCADE in MySQL?

Thanks.

possible duplicate of [How do I use cascade delete with SQL Server?](http://stackoverflow.com/questions/6260688/how-do-i-use-cascade-delete-with-sql-server) — Nikhil Talreja, Jun 26 '14 at 07:03

score 0 · Answer 1 · answered Jun 26 '14 at 07:04

0

You will need to

drop the existing foreign key constraint add a new one with the ON DELETE CASCADE setting enabled

answered Jun 26 '14 at 07:04

Nikhil Talreja

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Thanks. But can i disable the "ON DELETE CASCADE" once added without being removed??? – Vimal Raj Jun 26 '14 at 12:26
ON DELETE CASCADE is part of a constraint, so it can't be disabled separately. You need to disable the constraint itself. – Nikhil Talreja Jun 26 '14 at 12:30
Thanks alot Nikhil Talreja. :-) :-D – Vimal Raj Jun 26 '14 at 12:41

score 0 · Accepted Answer · answered Jun 26 '14 at 07:09

Create new foreign key constraint using :

CREATE TABLE table_name
(
  column1 datatype null/not null,
  column2 datatype null/not null,
  ...

  CONSTRAINT fk_column
     FOREIGN KEY (column1, column2, ... column_n)
     REFERENCES parent_table (column1, column2, ... column_n)
     ON DELETE CASCADE
);

or alter the existing constraint:

ALTER TABLE table_name
ADD CONSTRAINT constraint_name
   FOREIGN KEY (column1, column2, ... column_n)
   REFERENCES parent_table (column1, column2, ... column_n)
   ON DELETE CASCADE;

Thanks. But can i disable the "ON DELETE CASCADE" once added without being removed??? — Vimal Raj, Jun 26 '14 at 12:25

MySQL ON DELETE CASCADE

2 Answers2