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* Bitwise operation
@ 2003-06-30 12:28 Rudi Starcevic <rudi@oasis.net.au>
0 siblings, 2 replies; 4+ messages in thread
From: Rudi Starcevic @ 2003-06-30 12:28 UTC (permalink / raw)
To: pgsql-sql
Hi,
I'm learning to use Postgresql's bitwise operator's as I'm interested
in building super fast search's based on user selections in web forms.
So far so good but I have just lost it a little so I thought I'd post.
Please growl at me if I'm asking on the wrong list :-)
I understand this:
SELECT 111 & 11 = 11
but not this
SELECT 1111 & 111 = 71
I was expecting the second example to be
SELECT 1111 & 111 = 111
Hmm ...
Maybe I should search on the web for some more info on how to
understand this logic.
Math was never my strongest I was always better at creative writing.
Any advice much appreciated.
Thanks
Best Regards
Rudi.
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Bitwise operation
@ 2003-06-30 12:36 Hubert Lubaczewski <hubert.lubaczewski@eo.pl>
parent: Rudi Starcevic <rudi@oasis.net.au>
1 sibling, 0 replies; 4+ messages in thread
From: Hubert Lubaczewski @ 2003-06-30 12:36 UTC (permalink / raw)
To: Rudi Starcevic <rudi@oasis.net.au>; +Cc: pgsql-sql
On Mon, 30 Jun 2003 22:28:15 +1000
"Rudi Starcevic" <rudi@oasis.net.au> wrote:
> SELECT 1111 & 111 = 71
> I was expecting the second example to be
> SELECT 1111 & 111 = 111
hmm ..:
let's see:
dec(1111) is bin(10001010111)
dec(111) is bin(00001101111)
so, when we'll "AND" them:
1111 : 10001010111
111 : 00001101111
-------------------
00001000111 : dec: 71
quite reasonable, isn't it?
depesz
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Bitwise operation
@ 2003-06-30 12:42 Bruno Wolff III <bruno@wolff.to>
parent: Rudi Starcevic <rudi@oasis.net.au>
1 sibling, 1 reply; 4+ messages in thread
From: Bruno Wolff III @ 2003-06-30 12:42 UTC (permalink / raw)
To: Rudi Starcevic <rudi@oasis.net.au>; +Cc: pgsql-sql
On Mon, Jun 30, 2003 at 22:28:15 +1000,
Rudi Starcevic <rudi@oasis.net.au> wrote:
>
> Hi,
>
> I'm learning to use Postgresql's bitwise operator's as I'm interested
> in building super fast search's based on user selections in web forms.
>
> So far so good but I have just lost it a little so I thought I'd post.
> Please growl at me if I'm asking on the wrong list :-)
>
> I understand this:
>
> SELECT 111 & 11 = 11
>
> but not this
>
> SELECT 1111 & 111 = 71
>
> I was expecting the second example to be
>
> SELECT 1111 & 111 = 111
In the above examples the numbers are decimal values.
Maybe you wanted to do something like the following:
area=> select b'1111' & b'0111';
?column?
----------
0111
(1 row)
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Bitwise operation
@ 2003-06-30 23:48 Rudi Starcevic <rudi@oasis.net.au>
parent: Bruno Wolff III <bruno@wolff.to>
0 siblings, 0 replies; 4+ messages in thread
From: Rudi Starcevic @ 2003-06-30 23:48 UTC (permalink / raw)
To: ; +Cc: pgsql-sql
Bruno,Hubert,
Thanks.
It's all crystal clear now.
Now I can keep moving on with my app.
If all goes well I hope to add a 'techdoc' on how to do this.
I've found documents from other DBMS on using Bitwise operations
but not PG.
Cheers
Rudi.
Bruno Wolff III wrote:
>On Mon, Jun 30, 2003 at 22:28:15 +1000,
> Rudi Starcevic <rudi@oasis.net.au> wrote:
>
>
>>Hi,
>>
>>I'm learning to use Postgresql's bitwise operator's as I'm interested
>>in building super fast search's based on user selections in web forms.
>>
>>So far so good but I have just lost it a little so I thought I'd post.
>>Please growl at me if I'm asking on the wrong list :-)
>>
>>I understand this:
>>
>>SELECT 111 & 11 = 11
>>
>>but not this
>>
>>SELECT 1111 & 111 = 71
>>
>>I was expecting the second example to be
>>
>>SELECT 1111 & 111 = 111
>>
>>
>
>In the above examples the numbers are decimal values.
>
>Maybe you wanted to do something like the following:
>
>area=> select b'1111' & b'0111';
> ?column?
>----------
> 0111
>(1 row)
>
>---------------------------(end of broadcast)---------------------------
>TIP 4: Don't 'kill -9' the postmaster
>
>
>
^ permalink raw reply [nested|flat] 4+ messages in thread
end of thread, other threads:[~2003-06-30 23:48 UTC | newest]
Thread overview: 4+ messages (download: mbox mbox.gz follow: Atom feed)
-- links below jump to the message on this page --
2003-06-30 12:28 Bitwise operation Rudi Starcevic <rudi@oasis.net.au>
2003-06-30 12:36 ` Hubert Lubaczewski <hubert.lubaczewski@eo.pl>
2003-06-30 12:42 ` Bruno Wolff III <bruno@wolff.to>
2003-06-30 23:48 ` Rudi Starcevic <rudi@oasis.net.au>
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