Why MYSQL IN keyword not considering NULL values

Question

I am using the following query:

select count(*) from Table1 where CurrentDateTime>\'2012-05-28 15:34:02.403504\' and Error not in (\'Timeout\',\'Connectio         


        

Answer 1

Sorry for posting twice in the same forum, but I want to illustrate another example:

I agree with @Wagner Bianchi in [2] in this forum when he says: << It’s very trick when dealing with data and subqueries>>

Moreover, this should NOT be the behavior, I think Mysql's designers are mistaken when they made this decision documented in [1]. The design should be different. Let me explain: You know that when comparing

select (2) not in (1, 4, 3);
    you will get:
        +----------------------+
        | (2) not in (1, 4, 3) |
        +----------------------+
        |                    1 |
        +----------------------+
        1 row in set (0.00 sec)

BUT if in the list you have at least one NULL then:

select (2) not in (1, NULL, 3);
    throws:
        +-------------------------+
        | (2) not in (1, NULL, 3) |
        +-------------------------+
        |                    NULL |
        +-------------------------+
        1 row in set (0.00 sec)
    This is pretty absurd.

We are not the first ones in getting confused by this. See [2]

References:

[1] http://dev.mysql.com/doc/refman/5.0/en/comparison-operators.html#function_in

[2] http://blog.9minutesnooze.com/sql-not-in-subquery-null/comment-page-1/#comment-86954