G-3190: Avoid using NATURAL JOIN.
Blocker
Changeability, Reliability
Reason
A natural join
joins tables on equally named columns. This may comfortably fit on first sight, but adding logging columns to a table (changed_by
, changed_date
) will result in inappropriate join conditions.
Example (bad)
| select d.department_name
,e.last_name
,e.first_name
from employees e
natural join departments d
order by d.department_name
,e.last_name;
|
| DEPARTMENT_NAME LAST_NAME FIRST_NAME
------------------------------ ------------------------- --------------------
Accounting Gietz William
Executive De Haan Lex
...
|
| alter table departments add modified_at date default on null sysdate;
alter table employees add modified_at date default on null sysdate;
select d.department_name
,e.last_name
,e.first_name
from employees e
natural join departments d
order by d.department_name
,e.last_name;
|
Example (good)
| select d.department_name
,e.last_name
,e.first_name
from employees e
join departments d
on (e.department_id = d.department_id)
order by d.department_name
,e.last_name;
|
| DEPARTMENT_NAME LAST_NAME FIRST_NAME
------------------------------ ------------------------- --------------------
Accounting Gietz William
Executive De Haan Lex
...
|