Yoav Apter <yo...@checkpoint.com> wrote:
> I have the following table:
>
> CREATE TABLE x ('col1', 'col2', 'col3')
> Create col1index on x ('col1')
>
> When I run this query: "select * from x where col1 is null" I see the index
> on x is used.
> When I run this query: "select * from x where col1 is NOT null" I see the
> index on x is not used.
Why is that suprising? Imagine you are given a book with an index at the end,
and are asked to enumerate all pages where a particular term does *not* appear.
Would an index be helpful in this task?
> How can indexes be used with "not null" queries?
They cannot.
--
Igor Tandetnik
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