uri redirect

If I understand your question you have webservers that hosts https://abc.com, but one of the subfolders (https://abc.com/def) is located on another server and all those requests should be sent to that one instead?

Easiest way would be to implement a ltm-policy. First create another pool which contains the sql-server. You then create a policy and add rules and actions to it. Your rules should be something like this:

1. If uri path starts with /def --> forward traffic to sql-server pool.
2. For all traffic --> forward traffic to webserver pool.

Then assign the policy to your virtual server (and remove the default pool which you probably have set up).

The iRule you got in the other answer has nothing to do with your question. It redirect users from http to https.