I want to create a trigger to send automatic emails to the mail addresses on personal table when there is a change on the other table like 'city' on SQL*Plus. But I could not find a way to create this trigger, could you please help me?
First: This is not SQLPlus but Oracle SQL we are talking here - and actually you do have to write PL/SQL code for that, like in any trigger in Oracle. But you can use SQLPlus for that - or SQLdeveloper or any other tool which poses as database client.
How to send mails in PL/SQL:
UTL_MAIL.SEND ('sender@myapp.com','receiver@yourapp.com',
message => 'this is the message',
subject => 'Warnung: message arriving');
But your DBA must have configured the SMTP server for the database and you need appropriate privileges to send a mail.