How to write the below query with parameter and is null

Question

Hi, I need to retrive the data if the parameter is passed on the field, else retrive all records whose field is null
Example
CREATE TABLE DEPT
       (DEPTNO NUMBER(2),
        DNAME VARCHAR2(14),
        LOC VARCHAR2(13) );
INSERT INTO DEPT VALUES (10, 'ACCOUNTING', 'NEW YORK');
INSERT INTO DEPT VALUES (20, 'RESEARCH',   'DALLAS');
insert into dept values (30, 'SALES',      'CHICAGO');
INSERT INTO DEPT VALUES (40, 'OPERATIONS', 'BOSTON');
alter table dept add(object_id number);
insert into dept values (50, 'OPERATIONS', 'BOSTON',1);
insert into dept values (60, 'OPERATIONS', 'BOSTON',1);
INSERT INTO DEPT VALUES (70, 'OPERATIONS', 'BOSTON',2);
select * from dept where object_id =:p_object_id
If i pass the object_id as 1 , it shloud retrive the values of dept with object_id 1, but if i dont pass the object_id, it should retrive all the records whose object_id is null
IF 1 is passed, as object id , it should retrive, 50, 60, if 1 is not passed as object_id it should retive 10,20,30,40
It works fine for me seperately as,
select * from dept where object_id =:p_object_id -- 1
select * from dept where object_id is null;
Is this possible to do in single query.
Thanks

Answer 1

SELECT *
FROM dept
WHERE object_id = :p_object_id
OR (object_id is null and :p_object_id is null)
is one approach.  It's a bit verbose but the meaning is clear.  If you can identify a value that would never appear in the data (-1 for example)
WHERE nvl( object_id, -1 ) = nvl(p_object_id, -1 );
Justin