ORA-01403: no data found

Pretty common oracle error. Raised when you are trying to fetch data from sql into a pl/sl variable and the sql does not return any data.
>> Using the data from this schema

 
SQL> SELECT COUNT(*)
  FROM scott_emp
  WHERE empno = 9999;
 
  COUNT(*)
----------
         0
 
SQL> DECLARE
   l_ename scott_emp.ename%TYPE;
   l_empno scott_emp.empno%TYPE := 9999;
BEGIN
   SELECT ename
     INTO l_ename
     FROM scott_emp
     WHERE empno = l_empno;
END;
/
 
DECLARE
*
ERROR at line 1:
ORA-01403: no DATA found
ORA-06512: at line 5

What to do next
1. Re-Raise it with a error message that provides more context.

DECLARE
   l_ename scott_emp.ename%TYPE;
   l_empno scott_emp.empno%TYPE := 9999;
BEGIN
   SELECT ename
     INTO l_ename
     FROM scott_emp
     WHERE empno = l_empno;
EXCEPTION
  WHEN no_data_found
   THEN raise_application_error(-20001,'No employee exists with employee id ' || l_empno);
END;
/
ERROR at line 1:
ORA-20001: No employee EXISTS WITH employee id 9999
ORA-06512: at line 11

2. Suppress the error if this is a valid business scenario and do the necessary processing.
Example CASE : If a user has a preference to display the numbers in local currency, convert the amount, else, display in USD.

 
CREATE OR REPLACE PROCEDURE p_calc_sales_metrics(
   p_user_id IN users.user_id%TYPE,
   p_profit  IN net_sales.profit%TYPE
) AS
  l_pref_currency user_prefs.pref_currency%TYPE;
  l_profit_local_amt net_sales.profit%TYPE;
BEGIN
 
---other code
 BEGIN
 
 SELECT pref_currency
   INTO l_pref_currency
  WHERE user_id = p_user_id
 
        l_cur_conv_factor := get_conv_rate('USD',l_pref_currency);
 
 
 exception
   WHEN no_data_found 
    THEN l_cur_conv_factor := 1;
 END;
 
--- other code..
 
 l_profit_local_amt :=  p_profit * l_cur_conv_factor;
 
 
END;
/

3. Functions, by design, do not raise the NO_DATA_FOUND exception, instead they return null to the calling program.

CREATE OR REPLACE FUNCTION STGDATA.f_get_ename(
   i_empno IN scott_emp.empno%TYPE
) RETURN scott_emp.ename%TYPE
AS
  l_ename scott_emp.ename%TYPE;
BEGIN
 
  SELECT ename
    INTO l_ename
    FROM scott_emp
   WHERE empno = i_empno;
 
  RETURN l_ename;  
 
END;
/
 
SQL> SELECT f_get_ename(7839) FROM dual;
 
F_GET_ENAME(7839)
---------------------
KING
 
SQL>  SELECT f_get_ename(9999) FROM dual;
 
F_GET_ENAME(9999)
-------------------------------------------
 
 
SQL> SELECT nvl(f_get_ename(9999),'NULL RETURNED') FROM dual;
 
NVL(F_GET_ENAME(9999),'NULLRETURNED')
------------------------------------------------
NULL RETURNED