NOT operator

Question

hi everyone, i am having problem with the not operator in oracle.
consider the following
WITH data AS
SELECT 'TAK' cd, 'PL' TYPE FROM dual UNION ALL
SELECT 'TAK' cd, NULL TYPE FROM dual
SELECT * FROM data WHERE NOT (cd = 'TAK' AND TYPE='PL')
the above is not returning anything. what i want to do is to exclude all rows with cd=TAK and TYPE=PL
the rest should be display. so the output should be
CD       TYPE
============
TAK      <NULL VALUE HERE>however, the query above is not doing that. how can i modify my query to exclude rows with cd=TAK and TYPE=PL but display the one that doesnt match this condition like
second row, cd=TAK and TYPE=null

Answer 1

Hi,
elmasduro wrote:
hi everyone, i am having problem with the not operator in oracle.
consider the following
WITH data AS
SELECT 'TAK' cd, 'PL' TYPE FROM dual UNION ALL
SELECT 'TAK' cd, NULL TYPE FROM dual
SELECT * FROM data WHERE NOT (cd = 'TAK' AND TYPE='PL')the above is not returning anything. what i want to do is to exclude all rows with cd=TAK and TYPE=PL
the rest should be display. so the output should be
CD       TYPE
============
TAK      <NULL VALUE HERE>however, the query above is not doing that. how can i modify my query to exclude rows with cd=TAK and TYPE=PL but display the one that doesnt match this condition like
second row, cd=TAK and TYPE=nullRemember, SQL uses 3-value logic.
Conditions can be TRUE, FALSE or UNKNOWN. Rows are returned if (and only if) the WHERE clause evaluates to TRUE.
If either cd or type is NULL, but the other variable is what the condition is checking for, then
WHERE NOT (cd = 'TAK' AND TYPE='PL')will evaluate to UNKNOWN, because
NULL = x     is always UNKNOWN, regardless of what x is,
TRUE AND UNKNOWN     is UNKNOWN, and
NOT UNKNOWN     is UNKNOWN.
See the truth tables in the SQL language manual:
http://docs.oracle.com/cd/E11882_01/server.112/e26088/conditions004.htm#sthref1938
If you want to equate NULL cds with something other than 'TAK', and to equate NULL types with something other than 'PL', here's one way to do it:
SELECT     *
FROM     data
WHERE     NVL (cd,   'OK') != 'TAK'
OR     NVL (type, 'OK') != 'PL'
;I find the condition above easier to understand than the condition below, but they get the same results.
SELECT     *
FROM     data
WHERE     NOT (    NVL (cd,   'OK') = 'TAK'
         AND      NVL (type, 'OK') = 'PL'
;