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Tips for ORA-02292 Constraint violation - child records found

Oracle Tips by Burleson Consulting

Question:  I defined a master/slave table with a constraint using the "on delete restrict" clause.  When I try to delete a row from the master table I get the Oracle error: ORA-02292: integrity constraint (user....) violated - child record found.

Answer: When you use the "on delete" syntax you have two choices "on delete restrict" and on delete cascade".  The error message will point you to the specific owner and constraint name:

ORA-02292: violated integrity constraint (owner.constraintname)- child record found

You might also see these related errors:

ORA-02290: check constraint (owner.constraintname) violated

ORA-02291: integrity constraint (owner.constraintname) violated - parent key not found

Avoiding ORA-02292 with ON DELETE

This explanation from John Garmany's book "Easy Oracle SQL" describes the process in detail:

Let?s create the constraint.

SQL> alter table emp
2 add (constraint job_fk foreign key (job_key)
3 references job (job_key)
4 on delete cascade);

Now, when INSERT or UPDATE the job key column in the EMP table, the foreign key constraint will check to insure that the job already exists in the JOB table (or at least the job key exist in the JOB table).

Foreign key constraints can also be disabled, enabled and dropped.

alter table emp disable constraint job_fk;

alter table emp enable constraint job_fk;

alter table emp drop constraint job_fk;


Now, let?s talk about the ON DELETE part of the constraint. When we created the foreign key constraint . we included ON DELETE SET NULL or ON DELETE CASCADE. This clause tells the database what to do with the child records when the parent record is deleted. In the example above, we created the job_fk constraint with ON DELETE CASCADE.

This will cause the database to cascade the deletes. If I go to the JOB table and DELETE a job, all the employees that have that job will also be deleted as the DELETE will cascade to the child rows.

If we use the ON DELETE SET NULL, then when we delete the parent record, the child records with that value will be set to NULL.
 

If you like Oracle tuning, see the book "Oracle Tuning: The Definitive Reference", with 950 pages of tuning tips and scripts. 

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.


 

 

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