select * from dual where sys_op_map_nonnull(null) = 'FF' ;
D
-
X

It does return a row on my 10.2.0.3

Am I confused?

I thought sys_op_map_nonnull(’any non-null value’) was supposed be ‘any non-null value’.

I can also guarantee to you that

select *
from dual
where sys_op_map_nonnull(null) = 'FF'

returns a row.

Now I think it’s doing something more subtle - it’s doing a mapping of anything you put in it so

select *
from dual
where sys_op_map_nonnull(null) = sys_op_map_nonnull('FF')

will not return a row… need to test.

Here is a quick test that I think demonstrates Michael’s point that sys_op_map_nonnull (col1) is the same as nvl(col1,’FF’):

  EDDIE@XE> CREATE TABLE t (
    2   col1  VARCHAR2(10),
    3   col2  VARCHAR2(10));

  Table created.

  EDDIE@XE> INSERT INTO t
    2       VALUES (NULL,
    3               NULL
    4              )
    5  /

  1 row created.

  EDDIE@XE> INSERT INTO t
    2       VALUES ('FF',
    3               'FF'
    4              )
    5  /

  1 row created.

  EDDIE@XE> INSERT INTO t
    2       VALUES ('Eddie',
    3               'Awad'
    4              )
    5  /

  1 row created.

  EDDIE@XE> SELECT NVL (col1, 'I am null') col1,
    2         NVL (col2, 'I am null') col2
    3    FROM t
    4   WHERE nvl(col1,'FF') = nvl(col2,'FF')
    5  /

  COL1       COL2
  ---------- ----------
  I am null  I am null
  FF         FF

  EDDIE@XE> SELECT NVL (col1, 'I am null') col1,
    2         NVL (col2, 'I am null') col2
    3    FROM t
    4   WHERE sys_op_map_nonnull (col1) = sys_op_map_nonnull (col2)
    5  /

  COL1       COL2
  ---------- ----------
  I am null  I am null
  FF         FF

So, if sys_op_map_nonnull (col1) did not act like nvl(col2,’FF’), Oracle would not return the row with the varchar2 value FF in both col1 and col2.

I think the explanation here is that sys_op_map_nonnull (’FF’) equals sys_op_map_nonnull (’FF’) but sys_op_map_nonnull (’FF’) does not equal ‘FF’:

  EDDIE@XE> SELECT *
    2  FROM dual
    3  where  sys_op_map_nonnull ('FF') = sys_op_map_nonnull ('FF')
    4  /

  D
  -
  X

  EDDIE@XE> SELECT *
    2  FROM dual
    3  where  sys_op_map_nonnull ('FF') = 'FF'
    4  /

  no rows selected

The thing it maps to is an internally stored FF, and I don’t think you can get this actual value stored for any type except RAW. Then, to deal with the problem of comparing raws when using sys_op_mapnonnull(), sys_op_mapnonnull(ff) returns a two-byte value which is 00ff, so sys_op_map_nonnull(ff) != ff.