Question

I get ORA-04091 Error while inserting data into table A. Table A records are refferencing other records in the same table 1:N.
Father records have fk_id = null and child records have fk not null.

create or replace trigger TRBI_A 
BEFORE INSERT ON A
for each row
BEGIN
  IF :new.fk_id IS NOT NULL then
     UPDATE A SET actualTS = CURRENT_TIMESTAMP WHERE id = :new.fk_id;
  END IF;
END;

ORA-04091: table name is mutating, trigger/function may not see it

The problem could is probably caused by trigger which tried to modify or query a table that is currently being modified by the statement that fired the trigger.
Does anyone know how to modify the trigger to have it correct?

Answer 1

You know what the problem is, so just read your code a little: you update the same table you are putting the trigger on.

I guess in your case you just need to put :NEW.actualTS:=current_timestamp, without using the update statement.