On 1/25/17, Richard Hipp <[email protected]> wrote:
> On 1/25/17, [email protected] <[email protected]> wrote:
>>
>> I get weird sql result with subselect too
>> select * from (select row_number(name) as id,name from example ) t where
>> id<=5
>>
>
> SQLite is invoking your row_number() function twice for each row -
> once for the return value and a second time when evaluating the "id<5"
> expression.
Further information:
The query optimizer is transforming your nested query into a single
query. You wrote:
SELECT * FROM (SELECT func(name) AS id, name FROM example) WHERE id<5;
Evaluated directly, this would require two separate queries. For
improved performance, SQLite "flattens" the inner query into the
second, like this:
SELECT func(name), name FROM example WHERE func(name)<5;
--
D. Richard Hipp
[email protected]
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