CREATE TABLE test (
pubdate  DATE,
compdate DATE,
valuecol NUMBER(5));

INSERT INTO test VALUES (TRUNC(SYSDATE), TRUNC(SYSDATE+300), 1);
INSERT INTO test VALUES (TRUNC(SYSDATE-300), TRUNC(SYSDATE), 9);
COMMIT;

SELECT * FROM test;

CREATE OR REPLACE PROCEDURE testproc (
StartDate DATE, EndDate DATE, DateType IN VARCHAR2) IS

 i PLS_INTEGER;
BEGIN
  SELECT valuecol
  INTO i
  FROM test
  WHERE DECODE(DateType, 'AA',compdate, 'BB', pubdate, compdate) <= EndDate
  AND DECODE(DateType, 'AA', compdate, 'BB', pubdate, compdate) >= StartDate;

  dbms_output.put_line(TO_CHAR(i));
END testproc;
/

set serveroutput on

exec testproc(TRUNC(SYSDATE), TRUNC(SYSDATE), 'BB');