MySQL触发器在建立时，报语法错的问题

delimiter $$
create trigger trg_delete_on_users before DELETE on users
for each row 
begin
    delete from authorities where username = old.username ;
    delete from user_action where user_name = old.username ;
end $$
delimiter ;

开头要使用的 delimiter $$ 来定义$$为分隔符，在末尾再把分隔符恢复为分号。否则，解释器遇到分号，就认为你SQL完结了，然后就报语法错了，坑爹不？？