[HELP] Please, help with a simple SELECT statment

[Alex Cosser]

> SELECT * FROM STUDENTS,TUTORS WHERE (STUDENTS.Tut_ID=TUTORS.Tut_ID or STUDENTS.Tut_ID
is null)

I think this produces a cartesian product on rows where STUDENTS.Tut_ID is
null

create table students ( st_id number, tut_id number);
insert into students values (1,'');
insert into students values (2,'1');
create table tutors ( tut_id number, tut_name varchar(10));
insert into tutors values (1,'Fred');
insert into tutors values (2,'Joe');
commit;

SQL> SELECT * FROM STUDENTS,TUTORS WHERE STUDENTS.Tut_ID = TUTORS.Tut_ID
(+);

ST_ID TUT_ID TUT_ID TUT_NAME
---------- ---------- ---------- ----------
2 1 1 Fred
1

1 SELECT * FROM STUDENTS,TUTORS
2* WHERE (STUDENTS.Tut_ID=TUTORS.Tut_ID or STUDENTS.Tut_ID is null)
SQL> /

ST_ID TUT_ID TUT_ID TUT_NAME
---------- ---------- ---------- ----------
1 1 Fred
2 1 1 Fred
1 2 Joe