Using Joins

I have tables a and b as follows,

SQL> select * from a
  2 /

         X Y
---------- ------------------------------

         1 A1
         2 A2
         3 A3
         4 A4
           A99

SQL> select * from b;

         X Y
---------- ------------------------------

         3 B3
         4 B4
         5 B5
         6 B6

Query1:

SQL> select a.x,count(b.x) from a , b where a.x = b.x(+) and a.x is not null group by a.x order by
a.x;

         X COUNT(B.X)
---------- ----------

         1          0
         2          0
         3          1
         4          1

Query2:

SQL> select a.x,count(b.x) from a LEFT OUTER JOIN b ON a.x = b.x and a.x is not null group by a.x
order by a.x;

         X COUNT(B.X)
---------- ----------

         1          0
         2          0
         3          1
         4          1
                    0

Question :
Since keyword (+) can be avoided if we use the ANSI equivalent keyword LEFT OUTER JOIN then why
there is a difference in the output using using (+) ( query1) and using LEFT OUTER JOIN (query2) ?

Regards Received on Sun May 31 2009 - 02:45:02 CDT