Sqlplus using stored procedures to update a row - oracle

Question

This is what I have so far. When I enter valid data and run it the table updates correctly. When I run it using author numbers that I know don't exist in the table it still runs, and doesn't output the exception statements. Does anyone know why my exceptions don't seem to be working. Any help would be appreciated thanks!
CREATE OR REPLACE PROCEDURE update_authorname
(selected_author_num IN NUMBER,
new_author_first IN CHAR,
new_author_last IN CHAR) AS
BEGIN
UPDATE author
SET author_first = new_author_first, author_last = new_author_last
WHERE author_num = selected_author_num;
EXCEPTION
WHEN NO_DATA_FOUND
THEN
DBMS_OUTPUT.PUT_LINE('No author with this number exists: ' || selected_author_num);
WHEN ROWTYPE_MISMATCH
THEN
DBMS_OUTPUT.PUT_LINE('Error: There was a row type mismatch when updating');
END;
/
This is what I used to call the procedure:
BEGIN
update_authorname(6,'Emma','White');
END;
/

Answer 1

An update statement doesn't throw an exception when the where clause isn't matched, it just fails silently. Instead, you need to check either:
The row exists before trying to update or
The update changed something.
1. The row exists
CREATE OR REPLACE PROCEDURE update_authorname
(selected_author_num IN NUMBER,
new_author_first IN CHAR,
new_author_last IN CHAR) AS
BEGIN
IF NOT EXISTS (SELECT 1 FROM author WHERE author_num = selected_author_num;
DBMS_OUTPUT.PUT_LINE('No author with this number exists: ' || selected_author_num);
ELSE
UPDATE author
SET author_first = new_author_first, author_last = new_author_last
WHERE author_num = selected_author_num;
EXCEPTION
WHEN ROWTYPE_MISMATCH
THEN
DBMS_OUTPUT.PUT_LINE('Error: There was a row type mismatch when updating');
END;
/
2. The update made changes
CREATE OR REPLACE PROCEDURE update_authorname
(selected_author_num IN NUMBER,
new_author_first IN CHAR,
new_author_last IN CHAR) AS
BEGIN
UPDATE author
SET author_first = new_author_first, author_last = new_author_last
WHERE author_num = selected_author_num;
IF ##ROWCOUNT <= 0
DBMS_OUTPUT.PUT_LINE('No author with this number exists: ' || selected_author_num);
EXCEPTION
WHEN ROWTYPE_MISMATCH
THEN
DBMS_OUTPUT.PUT_LINE('Error: There was a row type mismatch when updating');
END;
/
There are certainly other ways to achieve the same result, but these are the two most common.