I am trying to get all the rows with the specific session_id
and also that do not have '3223' for the group_with
column. So I have this SQL statement :
SELECT * FROM pr_cart WHERE session_id=203130570714 AND group_with != 3223
Which to me it looks fine, but for some reason it does not return anything.
In my table I have entries that should not meet the criteria. i.e.
session_id=203130570714 | group_with=3225
which should be returned. session_id=203130570714 | group_with=NULL
which should be returned. session_id=203130570714 | group_with=3223
which should not be returned.
I tried:
<>
instead of!=
NOT (group_with=3223)
group_with NOT LIKE '3223'
How can I get all the rows with the specified
session_id
and that also have a different number than 3223
for the group_with
edit session_id is varchar and group_with is int
NULL
is a special value which you must take special care of:SELECT * FROM pr_cart WHERE session_id="203130570714" AND
(group_with != 3223 OR group_with IS NULL)
General recommendation
Basically all operations, which involve
NULL
as one operand, yield NULL
as result.SELECT NULL + 5; # NULL
SELECT NULL * 5; # NULL
SELECT NULL NOT IN (234); # NULL
SELECT 5 IN (NULL); # NULL
NULL
will never be interpreted neither as true
nor as false
and is therefore literally useless for deciding if a row should be contained in the result set or not.
Whenever one has a column definition, which allows
NULL
values, one must take special care of these values.
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