MySQL删除级联

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.

Answer 1

You will need to

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

Answer 2

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;