How PL/SQL Exceptions Are Raised?

Answer

The PL/SQL exceptions can be raised in 4 ways. Either the user can raise them or they can be raised by the PL/SQL engine. They are as follows:

The PL/SQL runtime engine raised named system exception: These exceptions are raised automatically by the program. You cannot control when PL/SQL will raise a system exception.

The programmer raised named exception: The programmer can use an explicit call to the RAISE statement to raise a programmer-defined or system-named exception.

The programmer raised unnamed, programmer-defined exception: These are raised with an explicit call to the RAISE_APPLICATION_ERROR procedure in the DBMS_STANDARD package.

The programmer re-raised "current" exception: From within an exception handler, you can re-raise the same exception for propagation to the enclosing block.