pepe wrote:
> SQL does not use the equality comparison for null values, it uses 'IS
> NULL' instead. Convenient, isn't it? ;)
Right, because NULL really means "unknown", and SQL uses 3-valued logic,
so NULL == NULL actually returns NULL, not TRUE or FALSE -- that is, we
don't know whether the two NULL values are "really" equal. (Unlike in
Ruby, where nil and false are both false in a logical context, SQL NULL
is not FALSE.)
So, if I remember my SQL correctly:
NULL == TRUE yields FALSE
NULL == FALSE yields FALSE
NULL == NULL yields NULL
which is why it's necessary to have the special IS NULL syntax:
NULL IS NULL yields TRUE
>
> Apparently Rails' magic does not go as far as to check if the NIL
> value is one of the values in the array to generate the correct SQL
> statement so I think you'll have to do it yourself and generate a
> string such as:
>
> conditions = "org is null or org in ('ABC', 'XYZ')"
I think you're right. I don't see another good way to do it. I wonder,
though, if COALESCE() would be useful in certain cases.
>
> This should be so easy to implement that I am not sure why it has not
> already been done.
Interesting question. I've never needed this except as part of complex
queries where I'm already writing SQL anyway, but YMMV.
Best,
--
Marnen Laibow-Koser
http://www.marnen.org
[email protected]
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