Is it possible to designing your own functions? Or are all of them built in?

Answer 1

You can create your own functions and stored procedures in SQL.
Check this out: http://dev.mysql.com/doc/refman/5.7/en/create-procedure.html

Answer 2

yes you can.
SQL has special feature through which you can make your own function. it's called stored procedure. it's pretty easy and effective

Answer 3

Yes. You can provided that you remark them with a given procedures.

Answer 4

yes it is valid..but you should use pl/SQL.you will also find similar concepts in pl/sql

Answer 5

yaya u can,,