Обсуждение: Use of the LIMIT clause ?

I read on a website dedicated to MySQL, that the limit clause allows
someone to restrict the result of a query to a certain domain.
Exemple : "select id, title from movie order by id limit 3" -> only the
(here, first) 3 lines of the table
I did knew about this, but the author goes further about the "limit
N,P", which allows someone to get only results between the Nth and Pth
lines of the whole result...
I tried this with psql, but couldn't get anything but parse errors.
However, "\h select" does mention "LIMIT [count, all] {offset, START}"
So, is it possible or not ? And what's the correct syntax ?

Thanks

IIRC, the postgres syntax uses limit and offset for what rows to get
(ie LIMIT 1 OFFSET 10)

On Mon, 12 Mar 2001, Richard Bayet wrote:

> I read on a website dedicated to MySQL, that the limit clause allows
> someone to restrict the result of a query to a certain domain.
> Exemple : "select id, title from movie order by id limit 3" -> only the
> (here, first) 3 lines of the table
> I did knew about this, but the author goes further about the "limit
> N,P", which allows someone to get only results between the Nth and Pth
> lines of the whole result...
> I tried this with psql, but couldn't get anything but parse errors.
> However, "\h select" does mention "LIMIT [count, all] {offset, START}"
> So, is it possible or not ? And what's the correct syntax ?

Richard Bayet <bayet@enseirb.fr> writes:
> I did knew about this, but the author goes further about the "limit
> N,P", which allows someone to get only results between the Nth and Pth
> lines of the whole result...

Is that actually how MySQL interprets two parameters?  We treat them
as count and offset respectively, which definition I thought was the
same as MySQL's.

> I tried this with psql, but couldn't get anything but parse errors.

Works for me:

regression=# select unique1 from tenk1 limit 10;
 unique1
---------
    8800
    1891
    3420
    9850
    7164
    8009
    5057
    6701
    4321
    3043
(10 rows)

regression=# select unique1 from tenk1 limit 3,5;
 unique1
---------
    8009
    5057
    6701
(3 rows)

regression=#

What PG version are you running?

            regards, tom lane

Tom Lane a écrit :
>
> Richard Bayet <bayet@enseirb.fr> writes:
> > I did knew about this, but the author goes further about the "limit
> > N,P", which allows someone to get only results between the Nth and Pth
> > lines of the whole result...
>
> Is that actually how MySQL interprets two parameters?  We treat them
> as count and offset respectively, which definition I thought was the
> same as MySQL's.

Well, it looks like the web site I read the piece of information from
was mistaking...
But MySQL's syntax is different, as found on
http://www.mysql.com/doc/S/E/SELECT.html :
"SELECT [STRAIGHT_JOIN] [SQL_SMALL_RESULT] [SQL_BIG_RESULT]
[SQL_BUFFER_RESULT]
[...]
        [LIMIT [offset,] rows]"

>
> > I tried this with psql, but couldn't get anything but parse errors.
>
> Works for me:
>
> regression=# select unique1 from tenk1 limit 10;
>  unique1
> ---------
>     8800
>     1891
>     3420
>     9850
>     7164
>     8009
>     5057
>     6701
>     4321
>     3043
> (10 rows)
>
> regression=# select unique1 from tenk1 limit 3,5;
>  unique1
> ---------
>     8009
>     5057
>     6701
> (3 rows)
>
> regression=#
>
> What PG version are you running?

I'm using v.7.0.2, and the above examples worked for me :)
When I tried using the LIMIT clause the first times, to obtain the same
results, I would have tried "select unique1 from tenk1 limit 5,8", ie
"limit start, stop"
Then I would have got :
  unique1
 ---------
     4321
     3043
 (2 rows)

What I tried and didn't work was the same as "select unique1 from tenk1
limit 5,10" (in my mind, getting the five last rows)...

Thanks for your help

>
>                         regards, tom lane
>
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Spy <spy@joystick.fr> writes:
> Tom Lane a �crit :
>> Is that actually how MySQL interprets two parameters?  We treat them
>> as count and offset respectively, which definition I thought was the
>> same as MySQL's.

> But MySQL's syntax is different, as found on
> http://www.mysql.com/doc/S/E/SELECT.html :
> "SELECT [STRAIGHT_JOIN] [SQL_SMALL_RESULT] [SQL_BIG_RESULT]
> [SQL_BUFFER_RESULT]
> [...]
>         [LIMIT [offset,] rows]"

That's annoying; looks like we do it backwards from MySQL.  Can anyone
confirm that this is how MySQL behaves (maybe it's a typo on this
documentation page)?

Should we consider changing ours if it is different?  Are there any
other RDBMSes that implement two-parameter LIMIT?

            regards, tom lane

it's like
     SELECT *
     FROM :table
     WHERE :condition
     LIMIT :limit
     OFFSET :offset

Sherwin

bayet@enseirb.fr writes:
>I read on a website dedicated to MySQL, that the limit clause allows
>someone to restrict the result of a query to a certain domain.
>Exemple : "select id, title from movie order by id limit 3" -> only the
>(here, first) 3 lines of the table
>I did knew about this, but the author goes further about the "limit
>N,P", which allows someone to get only results between the Nth and Pth
>lines of the whole result...
>I tried this with psql, but couldn't get anything but parse errors.
>However, "\h select" does mention "LIMIT [count, all] {offset, START}"
>So, is it possible or not ? And what's the correct syntax ?
>
>Thanks
>
>
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