Integer primary key is by definition not null, so looking for a null value
on an index can't work. I guess there exists an optimization opportunity to
just return an emotional set, though it seems easier to not specify an
As to why it does a table scan, the primary key isn't a separate index. The
rowid primary key is part of the table itself.
On Jan 7, 2018 11:22 AM, "Luuk" <luu...@gmail.com> wrote:
> On 07-01-18 19:09, x wrote:
> >> Because reading the whole record (all 3 fields) is more expensive than
> >> just reading the index which has all the info you need to give a correct
> >> answer on 'SELECT ID FROM TBL WHERE ID IS NULL;'
> > Yes, but the covering index has 2 fields (X & ID). The pk has only 1
> field (ID) so why not use that, particularly in the case where ‘ORDER BY
> ID’ was included in the query?
> sorry, i do not know
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