Oracle 11g Release 2

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ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS';
CREATE TABLE tbl (key, flag) AS
  SELECT 'A',  1 FROM DUAL UNION ALL
  SELECT 'B',  2 FROM DUAL UNION ALL
  SELECT 'C',  3 FROM DUAL UNION ALL
  SELECT NULL, 4 FROM DUAL;
4 rows affected

CREATE PROCEDURE sp_name (
  v_key  IN  TBL.KEY%TYPE,
  v_flag OUT TBL.FLAG%TYPE
)
AS
BEGIN
  SELECT flag
  INTO   v_flag
  FROM   tbl
  WHERE  key=v_key;
EXCEPTION
  WHEN NO_DATA_FOUND THEN
    v_flag := -1;
END;
/
DECLARE
  v_flag TBL.FLAG%TYPE;
BEGIN
  sp_name('A', v_flag);
  DBMS_OUTPUT.PUT_LINE('A: ' || v_flag);
  sp_name('B', v_flag);
  DBMS_OUTPUT.PUT_LINE('B: ' || v_flag);
  sp_name('C', v_flag);
  DBMS_OUTPUT.PUT_LINE('C: ' || v_flag);
  sp_name('D', v_flag);
  DBMS_OUTPUT.PUT_LINE('D: ' || v_flag);
  sp_name(NULL, v_flag);
  DBMS_OUTPUT.PUT_LINE('NULL: ' || v_flag);
END;
/
1 rows affected

dbms_output:
A: 1
B: 2
C: 3
D: -1
NULL: -1

CREATE OR REPLACE PROCEDURE sp_name (
  v_key  IN  TBL.KEY%TYPE,
  v_flag OUT TBL.FLAG%TYPE
)
AS
BEGIN
  IF v_key IS NULL THEN
    v_flag := -1;
  ELSE
    SELECT flag
    INTO   v_flag
    FROM   tbl
    WHERE  key=v_key;
  END IF;
EXCEPTION
  WHEN NO_DATA_FOUND THEN
    v_flag := -1;
END;
/
DECLARE
  v_flag TBL.FLAG%TYPE;
BEGIN
  sp_name('A', v_flag);
  DBMS_OUTPUT.PUT_LINE('A: ' || v_flag);
  sp_name('B', v_flag);
  DBMS_OUTPUT.PUT_LINE('B: ' || v_flag);
  sp_name('C', v_flag);
  DBMS_OUTPUT.PUT_LINE('C: ' || v_flag);
  sp_name('D', v_flag);
  DBMS_OUTPUT.PUT_LINE('D: ' || v_flag);
  sp_name(NULL, v_flag);
  DBMS_OUTPUT.PUT_LINE('NULL: ' || v_flag);
END;
/
1 rows affected

dbms_output:
A: 1
B: 2
C: 3
D: -1
NULL: -1