Does Oracle PL/SQL have a standard ASSERT routine?
There isn't a built-in assertion procedure in SQL or PL/SQL, so you will have to write your own.

There are two ways of going about this. You can either manually raise an exception, as discussed in this Oracle article, or you can write a wrapper for the raise_application_error procedure, which is documented in the Oracle exception handling section of the documentation. 

I'll add that exceptions were designed for this kind of scenario, so you'd be better off taking your programmer hat off for a second &amp; using your DBA hat :)