Procedure never raise NO_DATA_FOUND Exception - sql

Question

i've created an procedure which increases salaries of peoples working in a department by a certain rate. the department number and the rate are assed as parameters for the procedure.
Now, the procedure works great when i specify the good departement number, but once i specify a false one, and i'm waiting for the NO_DATA_FOUND Exception to raise, it never happen. I searched tried many thing but didn't found the answer, so if you can help me i woul be really greatfull. Thank you !
Here is my code :
create or replace PROCEDURE AugmenteSalaire(numDepartement in departements.numerodepartement%TYPE, taux IN number) IS
p_nbreTotalSalaire employes.salaireemploye%type;
begin
SELECT sum(salaireemploye)
INTO p_nbreTotalSalaire
FROM employes
WHERE numerodepartement = numDepartement;
if taux > 0 AND taux <= 100 THEN
if p_nbreTotalSalaire < 150000 THEN
Update employes e
SET e.salaireemploye = e.salaireemploye + (e.salaireemploye * (taux * 0.01))
WHERE e.numerodepartement = numDepartement
AND NOT numeroemploye = (SELECT departements.chefdepartement from departements
WHERE departements.numerodepartement = numDepartement);
ELSE
DBMS_OUTPUT.PUT_LINE('Transaction refused : The salary sum cannot be above 150000');
END IF;
ELSE
DBMS_OUTPUT.PUT_LINE('The rate cannot be under 0 or aboce 100');
END IF;
Exception
WHEN NO_DATA_FOUND THEN
DBMS_OUTPUT.PUT_LINE('The department number provided is invalid, '||
'please enter a valid department number(DEP001 for example)');
end;

Answer 1

SELECT sum(salaireemploye)
INTO p_nbreTotalSalaire
FROM employes
WHERE numerodepartement = numDepartement;
In this query you are using SUM(). Now if there is no matching department, i.e. input "numDepartement" is a false department, sum(salaireemploye) is 0 (no such department, so nothing to add, so 0).
sum(salaireemploye) thus has a valid value, which is 0 here. Hence this will never raise a NO_DATA_FOUND exception