Replace no rows into 0

Question

Hi, I am new in this forum.
I am traying to sum several items from the same table using alias.
In some of the alias the filters could retiurn no rows result and when I sum this the results is a no rows exeption.
Is there any way to change this no row into a 0 value.
I've tried to use NVL but as the results aren´t nulls it doesn´t work.
Best Regards

Answer 1

Or
WITH t AS
     (SELECT ename, empno
        FROM scott.emp_test
       WHERE job = 'CLERK'
      UNION
      SELECT 'Nobody found', NULL
        FROM DUAL)
SELECT ename, empno
  FROM (SELECT ename, empno, COUNT (1) OVER () cpt
          FROM t)
WHERE (cpt > 1 AND ename != 'Nobody found') OR (cpt = 1)
SQL> WITH t AS
  2       (SELECT ename, empno
  3          FROM scott.emp_test
  4         WHERE job = 'CLERK'
  5        UNION
  6        SELECT 'Nobody found', NULL
  7          FROM DUAL)
  8  SELECT ename, empno
  9    FROM (SELECT ename, empno, COUNT (1) OVER () cpt
10            FROM t)
11   WHERE (cpt > 1 AND ename != 'Nobody found') OR (cpt = 1);
ENAME             EMPNO
ADAMS              7876
JAMES              7900
MILLER             7934
SMITH              7369
SQL> WITH t AS
  2       (SELECT ename, empno
  3          FROM scott.emp_test
  4         WHERE job = 'CLERKKKKKK'
  5        UNION
  6        SELECT 'Nobody found', NULL
  7          FROM DUAL)
  8  SELECT ename, empno
  9    FROM (SELECT ename, empno, COUNT (1) OVER () cpt
10            FROM t)
11   WHERE (cpt > 1 AND ename != 'Nobody found') OR (cpt = 1);
ENAME             EMPNO
Nobody found
SQL>
SQL>