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

sql oracle
Ula Krukar picture Ula Krukar · Oct 15, 2009 · Viewed 224.4k times · Source

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

Answer

Vincent Malgrat picture Vincent Malgrat · Oct 15, 2009

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...).

Related questions

Get list of all tables in Oracle?

How do I query an Oracle database to display the names of all tables in it?

Read More
How do I limit the number of rows returned by an Oracle query after ordering?

Is there a way to make an Oracle query behave like it contains a MySQL limit clause? In MySQL, I can do this: select * from sometable order by name limit 20,10 to get the 21st to the 30th rows (skip the …

Read More
Oracle SQL: Update a table with data from another table

Table 1: id name desc ----------------------- 1 a abc 2 b def 3 c adf Table 2: id name desc ----------------------- 1 x 123 2 y 345 In oracle SQL, how do I run an sql update query that can update Table 1 with Table 2's name and desc using …

Read More