Oracle左外部联接

Question

SELECT
    a,
    last_note_user,
    c,
    d,
    iso_src
FROM
    X
    CROSS JOIN Y
    CROSS JOIN Z
    LEFT OUTER JOIN W
        ON W.last_note_user = Z.userid
           AND W.user_ten = Y.iso_src

The above ANSI code fetch me 107 records,When I giving the same query without ANSI code it is fetching 875 records.The non ANSI query is below:

SELECT
    a,
    last_note_user,
    c,
    d,
    iso_src
FROM
    X,
    Y,
    Z,
    W
WHERE
    W.last_note_user = Z.userid(+)
    AND W.user_ten = Y.iso_src(+)

why there is difference in the two query with ANSI and without ANSI standards?? By answering the above query please help me out!!!

Answer 1

Your old-style query has the (+) symbols on the wrong side of the predicate. It should be:

SELECT
    a,
    last_note_user,
    c,
    d,
    iso_src
FROM
    X,
    Y,
    Z,
    W
WHERE
    W.last_note_user (+) = Z.userid
    AND W.user_ten (+) = Y.iso_src

But I wouldn't use the old-style syntax any more really.

Answer 2

OUTER JOINS with old ANSI-syntax are ambiguous, so who knows what the query optimizer understands with this.

If the first SQL is producing the right rows, forget about the ANSI version and move on.