How to add 'ON DELETE CASCADE' in ALTER TABLE statement

Question

I have a foreign key constraint in my table, I want to add ON DELETE CASCADE to it. I have tried this: ``` alter table child_table_name modify constraint fk_name foreign key (child_column_name) references parent_table_name (parent_column_name) on delete cascade; ``` Doesn't work. EDIT: Foreign key already exists, there are data in foreign key column. The error message I get after executing the statement: ``` ORA-02275: such a referential constraint already exists in the table ```

Accepted Answer

You can not add `ON DELETE CASCADE` to an already existing constraint. You will have to `drop` and re-`create` the constraint. The documentation shows that the `MODIFY CONSTRAINT` clause can only modify the state of a constraint (i-e: `ENABLED/DISABLED`...).

How to add 'ON DELETE CASCADE' in ALTER TABLE statement

Solution

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