How do we update the table with the SQL trigger?

[irl]

How do we update the table with the SQL trigger? I'm updating the table. test_trigger which has a trigger to update the table table_forum♪ But I can't understand how to update it. table_forum if any data have changed test_trigger♪ How can the value be transferred to the trigger 1,000 and 200which I'm putting in the table test_trigger?

Updating. test_trigger:

UPDATE test_trigger SET test_name=1000  WHERE  test_name=200;

Here's the trigger of the table. test_trigger:

BEGIN
SET foreign_key_checks =  0 ; 
  UPDATE  table_forum  
  SET  forum2=как тут передать значение 1000 из UPDATE?  
  WHERE  forum2=как тут передать значение 200 из UPDATE?;
SET foreign_key_checks =  1 ;
END

Note: Trigger with AFTER parameter. I mean, first the table is updated. test_trigger and because table_forum♪

[Alberto]

We need to use the alias. NEW and OLD♪
OLD - it's a record before change.
NEW - it's a recording after change.

I mean, your option would be:

BEGIN
SET foreign_key_checks =  0 ; 
 UPDATE table_forum  SET forum2=NEW.test_name WHERE forum2=OLD.test_name
SET foreign_key_checks =  1 ;
END

It can be used as a trigger. BEFORE UPDATEand AFTER UPDATE