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Re: select contiguous addresses that start on a bit boundary




I should have said consecutive addresses, rather than contiguous.
I care about a set of consecutive addresses, and there is no guarantee
of record order.

On 12/17/2015 07:35 AM, John Stile wrote:
> I need help creating a select that returns 4 records that have
> contiguous addresses that start on a bit boundary.
>
> If 4 do not exist, I need a return of zero records.
>
> I would like to do this in one statement and I do not have ownership of
> this mysql server, so fancy views, temporary tables, indexing, etc are
> outside my permission level.
>
> I am also not the only consumer of this database, so altering it for my
> needs could hurt the other consumers.
>
> Below I specify the issue and where I am.
>
> Thank you for your attention.
>
> #
> # Create problem set
> # - This has non-contiguous addresses
> # - This has one status not 0
> # - This has contiguous addresses that start before the bit boundary
> #
> CREATE TABLE addresses ( address BIGINT(20), status INT );
> INSERT INTO addresses
> VALUES (100000000001,0),
>        (100000000003,0),
>        (100000000004,0),
>        (100000000005,1),
>        (100000000006,0),
>        (100000000007,0),
>        (100000000008,0),
>        (100000000009,0),
>        (100000000010,0),
>        (100000000011,0),
>        (100000000013,0),
>        (100000000014,0),
>        (100000000015,0),
>        (100000000016,0),
>        (100000000017,0);
> #
> # This shows the bit boundary, where the start is  (address & 3) = 0
> #
> select address, (address & 3) as boundary from addresses where address
>> 0 and status=0 order by address limit 10  ;
> +--------------+----------+
> | address      | boundary |
> +--------------+----------+
> | 100000000001 |        1 |
> | 100000000003 |        3 |
> | 100000000004 |        0 |
> | 100000000006 |        2 |
> | 100000000007 |        3 |
> | 100000000008 |        0 |
> | 100000000009 |        1 |
> | 100000000010 |        2 |
> | 100000000011 |        3 |
> | 100000000013 |        1 |
> +--------------+----------+
> 10 rows in set (0.00 sec)
> #
> # This shows contiguous add, but they do not stat on the bit  boundary
> #
> select c1.address, (address & 3) as boundary  from addresses c1 where 4
> = ( SELECT count(*) FROM addresses c2 WHERE c2.status = 0 and c2.address
> BETWEEN c1.address AND (c1.address + 3)  ) limit 10;
>
> +--------------+----------+
> | address      | boundary |
> +--------------+----------+
> | 100000000006 |        2 |
> | 100000000007 |        3 |
> | 100000000008 |        0 |
> | 100000000013 |        1 |
> | 100000000014 |        2 |
> +--------------+----------+
> 5 rows in set (0.00 sec)
>
>
>
> I can't seem to add my ((address & 3) = 0) condition to the correct location to get the desired
> result. I don't understand how I can use c1.address in the BETWEEN, and
> yet I can't seem to make ((address & 3) = 0) work anywhere.
>
>
>


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