SELECT Question

[Alex]

Hi,
I have a column with a sequence in a table and want to allocate the
first 200 for special purpose thus starting the sequence from 200. For
the first 200 I have entries that will be added and removed.

Is there an easy way to write a select statement that returns me the
frist free number or any within the range of 200?
For example if 1-30, and 32-50 are occupied then i would like to fill in
the new entry with id 31.
I currently do it with a function but I was just wondering if there is a
way without it..

Thanks
Alex





---------------------------(end of broadcast)---------------------------
TIP 6: Have you searched our list archives?

http://archives.postgresql.org

[Lada 'Ray' Lostak]

Re: SELECT Question

> Is there an easy way to write a select statement that returns me the[color=blue]
> frist free number or any within the range of 200?
> For example if 1-30, and 32-50 are occupied then i would like to fill in
> the new entry with id 31.
> I currently do it with a function but I was just wondering if there is a
> way without it..[/color]
If I understand well, what something about

SELECT min(xxx) FROM table WHERE xxx<50

Best regards,
Lada 'Ray' Lostak
Unreal64 Develop group

http://www.orcave.com

http://www.unreal64.net

--------------------------------------------------------------------------
In the 1960s you needed the power of two C64s to get a rocket
to the moon. Now you need a machine which is a vast number
of times more powerful just to run the most popular GUI.



---------------------------(end of broadcast)---------------------------
TIP 8: explain analyze is your friend

[Alex]

Re: SELECT Question

Thanks,
but that only gives me smallest number of the ones in use but not the
first free number.
Alex


Lada 'Ray' Lostak wrote:
[color=blue][color=green]
>>Is there an easy way to write a select statement that returns me the
>>frist free number or any within the range of 200?
>>For example if 1-30, and 32-50 are occupied then i would like to fill in
>>the new entry with id 31.
>>I currently do it with a function but I was just wondering if there is a
>>way without it..
>>
>>[/color]
>If I understand well, what something about
>
> SELECT min(xxx) FROM table WHERE xxx<50
>
>Best regards,
>Lada 'Ray' Lostak
>Unreal64 Develop group
>http://www.orcave.com
>http://www.unreal64.net
>
>
>--------------------------------------------------------------------------
>In the 1960s you needed the power of two C64s to get a rocket
>to the moon. Now you need a machine which is a vast number
>of times more powerful just to run the most popular GUI.
>
>
>
>
>
>[/color]



---------------------------(end of broadcast)---------------------------
TIP 2: you can get off all lists at once with the unregister command
(send "unregister YourEmailAddres sHere" to majordomo@postg resql.org)

[Manfred Koizar]

Re: SELECT Question

On Thu, 20 Nov 2003 16:52:37 +0900, Alex <alex@meerkatso ft.com> wrote:[color=blue][color=green][color=darkred]
>>>>Is there an easy way to write a select statement that returns me the
>>>>frist free number or any within the range of 200?
>>>>For example if 1-30, and 32-50 are occupied then i would like to fill in
>>>>the new entry with id 31.[/color][/color][/color]

Fortunately this is not the performance mailing list :-)

First free number:
SELECT max(t1.id) + 1
FROM t AS t1 INNER JOIN t AS t2
ON (t1.id < 200 AND t1.id < t2.id AND t2.id <= 200)
GROUP BY t2.id
HAVING max(t1.id) + 1 < t2.id
ORDER BY t2.id
LIMIT 1;

Make sure that there is always a row with id=0 and a row with id=200.

Any free number:
SELECT id - 1
FROM t
WHERE 1 < id AND id <= 200
AND NOT EXISTS (SELECT * FROM t AS t2 WHERE t2.id = t.id - 1)
LIMIT 1;

Always having a row with id=200 helps avoid unwanted corner cases.

One more:
SELECT coalesce(max(id ), 0) + 1
FROM t
WHERE id <= 200
AND id = (SELECT count(*) FROM t AS t2 WHERE t2.id <= t.id);

This should work without any dummy rows. And it will not work, if id
is not unique or there is any row with id < 1.

Servus
Manfred

---------------------------(end of broadcast)---------------------------
TIP 3: if posting/reading through Usenet, please send an appropriate
subscribe-nomail command to majordomo@postg resql.org so that your
message can get through to the mailing list cleanly

[Lada 'Ray' Lostak]

Re: SELECT Question

> > Is there an easy way to write a select statement that returns me the[color=blue][color=green]
> > frist free number or any within the range of 200?
> > For example if 1-30, and 32-50 are occupied then i would like to fill in
> > the new entry with id 31.
> > I currently do it with a function but I was just wondering if there is a
> > way without it..[/color]
> If I understand well, what something about
>
> SELECT min(xxx) FROM table WHERE xxx<50
>[/color]
After I sent it, I saw I understand bad... Just woke up... Sorry :)

I personally think, you need small procedure do to that, because you want to
perform condition 'min(xxx)' on "unexisting " columns.

R.


---------------------------(end of broadcast)---------------------------
TIP 7: don't forget to increase your free space map settings

[Alex]

Re: SELECT Question

yes i am doing it that way now, but though there may be another way ...
more out of curiosity

thanks anyway

Lada 'Ray' Lostak wrote:
[color=blue][color=green][color=darkred]
>>>Is there an easy way to write a select statement that returns me the
>>>frist free number or any within the range of 200?
>>>For example if 1-30, and 32-50 are occupied then i would like to fill in
>>>the new entry with id 31.
>>>I currently do it with a function but I was just wondering if there is a
>>>way without it..
>>>
>>>[/color]
>>If I understand well, what something about
>>
>> SELECT min(xxx) FROM table WHERE xxx<50
>>
>>
>>[/color]
>After I sent it, I saw I understand bad... Just woke up... Sorry :)
>
>I personally think, you need small procedure do to that, because you want to
>perform condition 'min(xxx)' on "unexisting " columns.
>
>R.
>
>
>---------------------------(end of broadcast)---------------------------
>TIP 7: don't forget to increase your free space map settings
>
>
>
>[/color]



---------------------------(end of broadcast)---------------------------
TIP 8: explain analyze is your friend

[Kris Jurka]

Re: SELECT Question



On Thu, 20 Nov 2003, Alex wrote:[color=blue][color=green][color=darkred]
> >>Is there an easy way to write a select statement that returns me the
> >>frist free number or any within the range of 200?
> >>For example if 1-30, and 32-50 are occupied then i would like to fill in
> >>the new entry with id 31.[/color][/color][/color]

If you had a table with an id column and 200 rows 1-200 you could do

SELECT MIN(idtab.id) FROM idtab LEFT JOIN realtab ON (idtab.id =
realtab.id AND realtab.id IS NULL)

A useful generic function would be one something like range(min,max) that
would return a set of rows so you wouldn't have to actually have a table.

Kris Jurka


---------------------------(end of broadcast)---------------------------
TIP 8: explain analyze is your friend

[Joe Conway]

Re: SELECT Question

Kris Jurka wrote:[color=blue]
> A useful generic function would be one something like range(min,max) that
> would return a set of rows so you wouldn't have to actually have a table.
>[/color]

You mean like this?

CREATE OR REPLACE FUNCTION test(int,int) RETURNS SETOF int AS '
BEGIN
FOR i IN $1..$2 LOOP
RETURN NEXT i;
END LOOP;
RETURN;
END;
' LANGUAGE 'plpgsql' STRICT IMMUTABLE;

regression=# select * from test(4, 8);
test
------
4
5
6
7
8
(5 rows)

HTH,

Joe



---------------------------(end of broadcast)---------------------------
TIP 7: don't forget to increase your free space map settings

[Manfred Koizar]

Re: SELECT Question

On Thu, 20 Nov 2003 16:52:37 +0900, Alex <alex@meerkatso ft.com> wrote:[color=blue][color=green][color=darkred]
>>>>Is there an easy way to write a select statement that returns me the
>>>>frist free number or any within the range of 200?
>>>>For example if 1-30, and 32-50 are occupied then i would like to fill in
>>>>the new entry with id 31.[/color][/color][/color]

Fortunately this is not the performance mailing list :-)

First free number:
SELECT max(t1.id) + 1
FROM t AS t1 INNER JOIN t AS t2
ON (t1.id < 200 AND t1.id < t2.id AND t2.id <= 200)
GROUP BY t2.id
HAVING max(t1.id) + 1 < t2.id
ORDER BY t2.id
LIMIT 1;

Make sure that there is always a row with id=0 and a row with id=200.

Any free number:
SELECT id - 1
FROM t
WHERE 1 < id AND id <= 200
AND NOT EXISTS (SELECT * FROM t AS t2 WHERE t2.id = t.id - 1)
LIMIT 1;

Always having a row with id=200 helps avoid unwanted corner cases.

One more:
SELECT coalesce(max(id ), 0) + 1
FROM t
WHERE id <= 200
AND id = (SELECT count(*) FROM t AS t2 WHERE t2.id <= t.id);

This should work without any dummy rows. And it will not work, if id
is not unique or there is any row with id < 1.

Servus
Manfred

---------------------------(end of broadcast)---------------------------
TIP 3: if posting/reading through Usenet, please send an appropriate
subscribe-nomail command to majordomo@postg resql.org so that your
message can get through to the mailing list cleanly

[Joe Conway]

Re: SELECT Question

Kris Jurka wrote:[color=blue]
> A useful generic function would be one something like range(min,max) that
> would return a set of rows so you wouldn't have to actually have a table.
>[/color]

You mean like this?

CREATE OR REPLACE FUNCTION test(int,int) RETURNS SETOF int AS '
BEGIN
FOR i IN $1..$2 LOOP
RETURN NEXT i;
END LOOP;
RETURN;
END;
' LANGUAGE 'plpgsql' STRICT IMMUTABLE;

regression=# select * from test(4, 8);
test
------
4
5
6
7
8
(5 rows)

HTH,

Joe



---------------------------(end of broadcast)---------------------------
TIP 7: don't forget to increase your free space map settings

[Tom Lane]

Re: SELECT Question

Joe Conway <mail@joeconway .com> writes:[color=blue]
> Kris Jurka wrote:[color=green]
>> A useful generic function would be one something like range(min,max) that
>> would return a set of rows so you wouldn't have to actually have a table.[/color][/color]
[color=blue]
> You mean like this?[/color]
[color=blue]
> CREATE OR REPLACE FUNCTION test(int,int) RETURNS SETOF int AS '
> BEGIN
> FOR i IN $1..$2 LOOP
> RETURN NEXT i;
> END LOOP;
> RETURN;
> END;
> ' LANGUAGE 'plpgsql' STRICT IMMUTABLE;[/color]

I was thinking of proposing that we provide something just about like
that as a standard function (written in C, not in plpgsql, so that it
would be available whether or not you'd installed plpgsql). There are
some places in the information_sch ema that desperately need it ---
right now, the value of FUNC_MAX_ARGS is effectively hard-wired into
some of the information_sch ema views, which means they are broken if
one changes that #define. We could fix this if we had a function like
the above and exported FUNC_MAX_ARGS as a read-only GUC variable.

regards, tom lane

---------------------------(end of broadcast)---------------------------
TIP 6: Have you searched our list archives?

http://archives.postgresql.org

[Joe Conway]

Re: SELECT Question

Tom Lane wrote:[color=blue]
> Joe Conway <mail@joeconway .com> writes:[color=green]
>>CREATE OR REPLACE FUNCTION test(int,int) RETURNS SETOF int AS '
>>BEGIN
>> FOR i IN $1..$2 LOOP
>> RETURN NEXT i;
>> END LOOP;
>> RETURN;
>>END;
>>' LANGUAGE 'plpgsql' STRICT IMMUTABLE;[/color]
>
> I was thinking of proposing that we provide something just about like
> that as a standard function (written in C, not in plpgsql, so that it
> would be available whether or not you'd installed plpgsql). There are
> some places in the information_sch ema that desperately need it ---
> right now, the value of FUNC_MAX_ARGS is effectively hard-wired into
> some of the information_sch ema views, which means they are broken if
> one changes that #define. We could fix this if we had a function like
> the above and exported FUNC_MAX_ARGS as a read-only GUC variable.[/color]

I've been really busy on other-than-postgres stuff lately, but I'm
planning to carve out time next week to start doing some 7.5
development. I'll take this one if you want.

Joe


---------------------------(end of broadcast)---------------------------
TIP 4: Don't 'kill -9' the postmaster

[Alex]

Re: SELECT Question

All,
thanks for the many suggestions
Alex

Manfred Koizar wrote:
[color=blue]
>On Thu, 20 Nov 2003 16:52:37 +0900, Alex <alex@meerkatso ft.com> wrote:
>
>[color=green][color=darkred]
>>>>>Is there an easy way to write a select statement that returns me the
>>>>>frist free number or any within the range of 200?
>>>>>For example if 1-30, and 32-50 are occupied then i would like to fill in
>>>>>the new entry with id 31.
>>>>>
>>>>>[/color][/color]
>
>Fortunately this is not the performance mailing list :-)
>
>First free number:
>SELECT max(t1.id) + 1
> FROM t AS t1 INNER JOIN t AS t2
> ON (t1.id < 200 AND t1.id < t2.id AND t2.id <= 200)
> GROUP BY t2.id
>HAVING max(t1.id) + 1 < t2.id
> ORDER BY t2.id
> LIMIT 1;
>
>Make sure that there is always a row with id=0 and a row with id=200.
>
>Any free number:
>SELECT id - 1
> FROM t
> WHERE 1 < id AND id <= 200
> AND NOT EXISTS (SELECT * FROM t AS t2 WHERE t2.id = t.id - 1)
> LIMIT 1;
>
>Always having a row with id=200 helps avoid unwanted corner cases.
>
>One more:
>SELECT coalesce(max(id ), 0) + 1
> FROM t
> WHERE id <= 200
> AND id = (SELECT count(*) FROM t AS t2 WHERE t2.id <= t.id);
>
>This should work without any dummy rows. And it will not work, if id
>is not unique or there is any row with id < 1.
>
>Servus
> Manfred
>
>
>
>[/color]



---------------------------(end of broadcast)---------------------------
TIP 8: explain analyze is your friend