query "not equal" doesn't work

Question

I have very simple query like this:

SELECT * FROM `all_conversations` WHERE `deleted_1` != '1'; 

And my deleted_1 be default is null or some user id, but for some reason this query always returns me 0 rows, i also tried <> but still no luck what could be wrong?

EDTI So after running more querys i find out that my problems was default value of deleted_1 field, it was NULL so i modified my query and now it works fine:

SELECT * FROM `all_conversations` WHERE `deleted_1` != 'NULL' AND `deleted_1` != 23 

Answer 1

SELECT * FROM all_conversations WHERE deleted_1 <> 1 OR deleted_1 IS NULL 

NULL values need special treatment: http://dev.mysql.com/doc/refman/5.1/en/working-with-null.html

I'd suggest using the diamond operator (<>) in favor of != as the first one is valid SQL and the second one is a MySQL addition.

Answer 2

I recommend to use NULL-safe operator and negation

SELECT * FROM `all_conversations` WHERE NOT(`deleted_1` <=> '1');