when to use with as, when to use declare cursor for

Hallo everyone,

I understand how DB2 internally operates with as and declare cursor for. As in the documentation stated:
1. with as is aiming the pre-select operation before the usually bigger select statment.
2. declare cursor for -> a real table stored temporarily. Often used to load statement.

So far so good. I am wondering what the real differences between the two, because I can make use of them vise and versa for my sql codes.

Thank you.

Regards,
Ratna:)