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* Re: [SQL] perl and postgres. . .
@ 1999-04-21 15:02 Gene Selkov Jr. <selkovjr@xnet.com>
parent: JT Kirkpatrick <jt-kirkpatrick@mpsllc.com>
1 sibling, 0 replies; 4+ messages in thread
From: Gene Selkov Jr. @ 1999-04-21 15:02 UTC (permalink / raw)
To: JT Kirkpatrick <jt-kirkpatrick@mpsllc.com>; pgsql-interfaces@hub.org
> I'm trying in perl to get a maximum value from a field in a postgres table:
> $query="select max(userseq) from dataentry;";
> $result=$conn->exec("$query");
>
> and then capture that value in a scalar variable:
> $userseq=($result);
>
> but it's not working.
$result->getvalue(0, 0)
(pse. read examples in `perldoc Pg`)
^ permalink raw reply [nested|flat] 4+ messages in thread
* perl and postgres. . .
@ 1999-04-21 15:45 JT Kirkpatrick <jt-kirkpatrick@mpsllc.com>
0 siblings, 2 replies; 4+ messages in thread
From: JT Kirkpatrick @ 1999-04-21 15:45 UTC (permalink / raw)
To: 'pgsql-interfaces@hub.org' <pgsql-interfaces@hub.org>; 'pgsql-sql@hub.org' <pgsql-sql@hub.org>; 'chugalug@listserv.highertech.net' <chugalug@listserv.highertech.net>
I'm trying in perl to get a maximum value from a field in a postgres table:
$query="select max(userseq) from dataentry;";
$result=$conn->exec("$query");
and then capture that value in a scalar variable:
$userseq=($result);
but it's not working. The field userseq is int4 if that matters to you.
if I can capture that value in a variable then I can use it in an update
query for that particular record. Can anyone enlighten me??
jt
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: [SQL] perl and postgres. . .
@ 1999-04-21 19:10 Brett W. McCoy <bmccoy@lan2wan.com>
parent: JT Kirkpatrick <jt-kirkpatrick@mpsllc.com>
1 sibling, 0 replies; 4+ messages in thread
From: Brett W. McCoy @ 1999-04-21 19:10 UTC (permalink / raw)
To: JT Kirkpatrick <jt-kirkpatrick@mpsllc.com>; +Cc: 'pgsql-interfaces@hub.org' <pgsql-interfaces@hub.org>; 'pgsql-sql@hub.org' <pgsql-sql@hub.org>; 'chugalug@listserv.highertech.net' <chugalug@listserv.highertech.net>
On Wed, 21 Apr 1999, JT Kirkpatrick wrote:
> I'm trying in perl to get a maximum value from a field in a postgres table:
> $query="select max(userseq) from dataentry;";
> $result=$conn->exec("$query");
>
> and then capture that value in a scalar variable:
> $userseq=($result);
>
> but it's not working. The field userseq is int4 if that matters to you.
> if I can capture that value in a variable then I can use it in an update
> query for that particular record. Can anyone enlighten me??
You can't get row information from a query that way. You need to use
$result->fetchrow to get the actual data out of your query (it returns
Null if there are no more rows to fetch from). You could do something like:
@q_row = $result->fetchrow;
$userseq = $q_row[0];
To get that information.
Brett W. McCoy
http://www.lan2wan.com/~bmccoy
-----------------------------------------------------------------------
Self Test for Paranoia:
You know you have it when you can't think of anything that's
your own fault.
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: [SQL] perl and postgres. . .
@ 1999-04-21 19:36 Gene Selkov, Jr. <selkovjr@mcs.anl.gov>
0 siblings, 0 replies; 4+ messages in thread
From: Gene Selkov, Jr. @ 1999-04-21 19:36 UTC (permalink / raw)
To: JT Kirkpatrick <jt-kirkpatrick@mpsllc.com>; pgsql-interfaces@hub.org
> I am trying
> $query="select max((userseq) from dataentry;";
> $result=$conn->exec("$query");
> $userseq=($result->getvalue(0,0));
>
> * I need the value in a variable name other than $result. . .
>
> If I try
> $query="select max((userseq) from dataentry;";
> $result->getvalue(0,0);
> $userseq=$result;
>
> it bombs. Ahhh, the frustrations of being new to this!
Now I see what your problem is. You missed the whole point. $result is
not a variable, it is an object reference, so is $conn. The exec()
method of $conn (or rather, that of the object referenced by $conn)
returns the result object. You normally access the object's data
through its methods, in this case, getvalue(), fetchrow(), etc. -- see
the Pg doc for the full list.
So the following simply copies the reference to the result object into
$userseq, and that may bomb, depending on how you use it further:
> $userseq=$result;
The following the value you need, but it since there is no explicit
assignment, it is getting lost:
> $result->getvalue(0,0);
What you needed was
$userseq = $result->getvalue(0,0);
And again, the manual for Pg has complete examples. Note the code you
need to add to check for errors that may result from each method call.
--Gene
^ permalink raw reply [nested|flat] 4+ messages in thread
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-- links below jump to the message on this page --
1999-04-21 15:45 perl and postgres. . . JT Kirkpatrick <jt-kirkpatrick@mpsllc.com>
1999-04-21 15:02 ` Gene Selkov Jr. <selkovjr@xnet.com>
1999-04-21 19:10 ` Brett W. McCoy <bmccoy@lan2wan.com>
1999-04-21 19:36 Re: [SQL] perl and postgres. . . Gene Selkov, Jr. <selkovjr@mcs.anl.gov>
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