Then the where clause you have matches no rows.

Probably because of this:

IF @ADR3 IS NULL

SELECT ADR1, ADR2, POSTAL_CODE

FROM PAT_NAMES_ADDRESS

WHERE CURRENT_ONE = RTRIM(@CURRENT_ONE)

AND ADR1 = RTRIM(@ADR1)

AND ADR2 = RTRIM(@ADR2)

AND ADR3 = RTRIM(@ADR3)

AND POSTAL_CODE = RTRIM(@POSTAL_CODE)

As mentioned earlier in this thread, Column = NULL will return no rows (because NULL is never = to anything). You've run an IF checking whether or not @ADR3 IS NULL and if it is you're running a select which looks for rows WHERE ADR3 = NULL, which is never true.

Might be worth doing some reading on NULL handling in SQL.