This rule applies whenever an `+IF+` statement is followed by one or more `+ELSEIF+` statements; the final `+ELSEIF+` should be followed by an `+ELSE+` statement.
The requirement for a final `+ELSE+` statement is defensive programming.
The `+ELSE+` statement should either take appropriate action or contain a suitable comment as to why no action is taken. This is consistent with the requirement to have a final `+OTHER+` clause in a `+SELECT+` statement.
