Oracle SQL触发器不起作用

Question

I have a very simple trigger, that prints out the username and date when a new row is inserted into the users table. But after it successfully compiled, the trigger didn't get triggered (there was no output in the dbms window). So, I simplified my code until I got this:

CREATE OR REPLACE TRIGGER logger
AFTER INSERT ON USERS
BEGIN
   DBMS_OUTPUT.PUT_LINE('User added with name:');
END;

If I run the code in the SQL worksheet (from BEGIN to END), I can see the output, but not when I try to use the trigger. Where is the problem?

Answer 1

There are two options, one is that the trigger is not firing, the other is that it is, but you're not seeing the output.

1. Assuming you're working in a console program like sqlplus, make sure to do SET SERVEROUTPUT ON before inserting your row.

2. If that doesn't fix it, then make sure the trigger is firing. Try creating a simple table:

   CREATE TABLE logtable ( msg VARCHAR2(30 CHAR));

Next, add this to your trigger,

INSERT INTO logtable( msg ) VALUES ( 'trigger fired' );

Then, try your insert again.