Bug in JOIN syntax? (oracle 9i)

Question

Hi,
take these three tables:
MASTER (id NUMBER, name VARCHAR2(10))
DETAIL (id NUMBER, master_id NUMBER)
SUBDETAIL (id NUMBER, detail_id NUMBER, name VARCHAR(10)
When I perform this query:
SELECT SUBDETAIL.id as did, MASTER.id as mid
FROM SUBDETAIL
JOIN DETAIL ON (SUBDETAIL.detail_id = DETAIL.id)
JOIN MASTER ON (DETAIL.master_id = MASTER.id)
WHERE
name = 'joe';
I would expect the parser to give me 'column ambiguously defined' (because the 'name' field from the whereclause is defined in both subdetail and master).
However, it does not say that. Instead, it assumes that it should use the name field from master. This is confusing, as this could easily lead to mistakes (as it did in my application)
Greetings,
Ivo

Answer 1

There seems to be a difference between the way Oracle resolves column names using the ANSI join syntax and Oracle's syntax. It appears that Oracle does not know about the columns, until it processes each join, and further, the last table joined seems to be sued to resolve nameing conflicts. Consider:
SQL> SELECT * FROM master;
        ID NAME
         1 joe
SQL> SELECT * FROM subdetail;
        ID  DETAIL_ID NAME
         1          2 fred
SQL> SELECT * FROM detail;
        ID  MASTER_ID
         2          1
SQL> SELECT subdetail.id AS did, master.id AS mid
  2  FROM subdetail
  3       JOIN detail ON (subdetail.detail_id = detail.id)
  4       JOIN master ON (detail.master_id = master.id)
  5  WHERE name = 'joe';
       DID        MID
         1          1
SQL> SELECT subdetail.id AS did, master.id AS mid
  2  FROM subdetail
  3       JOIN detail ON (subdetail.detail_id = detail.id)
  4       JOIN master ON (detail.master_id = master.id)
  5  WHERE name = 'fred';
no rows selected
So, it is clearly going after master.name. However,
SQL> SELECT subdetail.id AS did, master.id AS mid
  2  FROM detail
  3       JOIN master ON (master.id = master_id)
  4       JOIN subdetail ON (subdetail.detail_id = detail.id)
  5  WHERE name = 'joe'
no rows selected
But,
SQL> SELECT subdetail.id AS did, master.id AS mid
  2  FROM detail
  3       JOIN subdetail ON (subdetail.detail_id = detail.id)
  4       JOIN master ON (master.id = master_id)
  5  WHERE name = 'joe'
       DID        MID
         1          1
Old style syntax gives:
SQL> SELECT subdetail.id AS did, master.id AS mid
  2  FROM subdetail, detail, master
  3  WHERE subdetail.detail_id = detail.id and
  4        detail.master_id = master.id and
  5        name = 'joe';
      name = 'joe'
ERROR at line 5:
ORA-00918: column ambiguously defined
and note that
SQL> SELECT subdetail.id AS did, master.id AS mid
  2  FROM subdetail
  3      JOIN master ON (detail.master_id = master.id)
  4      JOIN detail ON (subdetail.detail_id = detail.id)
  5  WHERE name = 'joe'
    JOIN master ON (detail.master_id = master.id)
ERROR at line 3:
ORA-00904: invalid column nameSo, in ANSI syntax, order matters, and whatever the syntax good testing matters.
TTFN
John