Oracle 18c

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CREATE TABLE emp (deptno, sal) AS
SELECT 1, 100 FROM DUAL UNION ALL
SELECT 1, 200 FROM DUAL UNION ALL
SELECT 1, 300 FROM DUAL UNION ALL
SELECT 2, 100 FROM DUAL UNION ALL
SELECT 2, 200 FROM DUAL UNION ALL
SELECT 3, 300 FROM DUAL;  
6 rows affected

CREATE TYPE number_list IS TABLE OF NUMBER;
DECLARE
  v_sal EMP.SAL%TYPE;
  v_deptnos number_list;
BEGIN
  SELECT AVG(sal)
       , CAST(COLLECT(DISTINCT deptno) AS number_list)
  INTO   v_sal
       , v_deptnos
  FROM   emp;

  DBMS_OUTPUT.PUT_LINE(v_sal);
  FOR i IN 1 .. v_deptnos.COUNT LOOP
    DBMS_OUTPUT.PUT_LINE(v_deptnos(i));
  END LOOP;
END;
/
1 rows affected

dbms_output:
200
1
2
3