mysql - Setting up a trigger in PHPMyAdmin -

i'm trying comprehend triggers, , think understand them, haven't been able implement of them. want code delete user name "test". if updates name "test" user should deleted.

my example code:

create trigger `my_trigger` before update on `my_db` each row begin delete my_table `username` = 'test'; end 

my error:

#1064 - have error in sql syntax; check manual corresponds mysql server version right syntax use near '' @ line 4  

i can't figure out why delete statement giving me error. ideas?

here syntaxically correct sql:

delimiter ; drop trigger if exists `my_trigger`; delimiter $$ create trigger `my_trigger` before update on `my_table` each row begin     delete my_table `username` = 'test'; end$$ delimiter; 

but won't work, because can't delete table, updating:

a trigger can access both old , new data in own table. trigger can affect other tables, not permitted modify table being used (for reading or writing) statement invoked function or trigger.

http://dev.mysql.com/doc/refman/5.5/en/faqs-triggers.html#qandaitem-b-5-1-9

if want simple example, try this:

delimiter ; drop trigger if exists `my_trigger`; delimiter $$ create trigger `my_trigger` before update on `my_table` each row begin     set new.`username` = 'aaa'; end$$ delimiter; 

this set 'aaa' user name when updating.