Thread: [GENERAL] libpq confusion
Hi, ALL, draft=# SELECT 1 FROM abcattbl WHERE abt_tnam = 'leagues';?column? ---------- (0 rows) However running it thru the PQexecParam() I am getting "PGRES_TUPLES_OK" which means that the such record exist. How do I properly check if the record exists from libpq? -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
2017-09-20 5:36 GMT+02:00 Igor Korot <ikorot01@gmail.com>:
Hi, ALL,
draft=# SELECT 1 FROM abcattbl WHERE abt_tnam = 'leagues';
?column?
----------
(0 rows)
However running it thru the PQexecParam() I am getting "PGRES_TUPLES_OK"
which means that the such record exist.
That means so this command doesn't fail - not so there are some record.
you can use different query, that returns true, false
SELECT EXISTS(SELECT * FROM abcattbl WHERE abt_tnam = 'leagues');
Regards
Pavel
How do I properly check if the record exists from libpq?
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>How do I properly check if the record exists from libpq? Igor, I use PQntuples() to check the number of ... tuples, for > 0 Allan ______________________________________________________________________ This e-mail message may contain confidential or legally privileged information and is only for the use of the intended recipient(s).Any unauthorized disclosure, dissemination, distribution, copying or the taking of any action in reliance onthe information herein is prohibited. E-mails are not secure and cannot be guaranteed to be error free as they can be intercepted,amended, or contain viruses. Anyone who communicates with us by e-mail is deemed to have accepted these risks.GFG Alliance Australia and its related bodies corporate and the sender are not responsible for errors or omissionsin this message and deny any responsibility for any damage arising from the use of this e-mail. Any opinion andother statement contained in this message and any attachment are solely those of the author and do not necessarily representthose of the company. All and any rights as to confidentiality, legal professional privilege and copyright are expresslyreserved. -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Hi, guys, On Wed, Sep 20, 2017 at 12:20 AM, Allan Harvey <allan.harvey@libertyonesteel.com> wrote: > >>How do I properly check if the record exists from libpq? > > Igor, > I use PQntuples() to check the number of ... tuples, for > 0 I was actually curious - isn't it what "PGRES_COMMAND_OK" for? IIUC, this constant indicates successful query run, but no records was generated. Or am I missing something and I will have to check PQntuples()? Thank you. > > Allan > > ______________________________________________________________________ > This e-mail message may contain confidential or legally privileged information and is only for the use of the intendedrecipient(s). Any unauthorized disclosure, dissemination, distribution, copying or the taking of any action in relianceon the information herein is prohibited. E-mails are not secure and cannot be guaranteed to be error free as theycan be intercepted, amended, or contain viruses. Anyone who communicates with us by e-mail is deemed to have acceptedthese risks. GFG Alliance Australia and its related bodies corporate and the sender are not responsible for errorsor omissions in this message and deny any responsibility for any damage arising from the use of this e-mail. Any opinionand other statement contained in this message and any attachment are solely those of the author and do not necessarilyrepresent those of the company. All and any rights as to confidentiality, legal professional privilege and copyrightare expressly reserved. -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
On 9/20/2017 6:30 AM, Igor Korot wrote:
Hi, guys, On Wed, Sep 20, 2017 at 12:20 AM, Allan Harvey <allan.harvey@libertyonesteel.com> wrote:How do I properly check if the record exists from libpq?Igor, I use PQntuples() to check the number of ... tuples, for > 0I was actually curious - isn't it what "PGRES_COMMAND_OK" for? IIUC, this constant indicates successful query run, but no records was generated. Or am I missing something and I will have to check PQntuples()?
a query that returns zero rows is still successful.
-- john r pierce, recycling bits in santa cruz
Hi, John, On Wed, Sep 20, 2017 at 12:02 PM, John R Pierce <pierce@hogranch.com> wrote: > On 9/20/2017 6:30 AM, Igor Korot wrote: > > Hi, guys, > > On Wed, Sep 20, 2017 at 12:20 AM, Allan Harvey > <allan.harvey@libertyonesteel.com> wrote: > > How do I properly check if the record exists from libpq? > > Igor, > I use PQntuples() to check the number of ... tuples, for > 0 > > I was actually curious - isn't it what "PGRES_COMMAND_OK" for? > IIUC, this constant indicates successful query run, but no records was > generated. > > Or am I missing something and I will have to check PQntuples()? > > > a query that returns zero rows is still successful. From the documentation: https://www.postgresql.org/docs/9.1/static/libpq-exec.html [quote] PGRES_COMMAND_OK Successful completion of a command returning no data. [/quote] No data = no rows, right? Thank you. > > -- > john r pierce, recycling bits in santa cruz -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
On 9/20/2017 10:34 AM, Igor Korot wrote:
>From the documentation: https://www.postgresql.org/docs/9.1/static/libpq-exec.html [quote] PGRES_COMMAND_OK Successful completion of a command returning no data. [/quote] No data = no rows, right?
from that same page, a bit farther down, clarifying the potentially confusing wording.
If the result status is PGRES_TUPLES_OK, then the functions described below can be used to retrieve the rows returned by the query. Note that a SELECT command that happens to retrieve zero rows still shows PGRES_TUPLES_OK. PGRES_COMMAND_OK is for commands that can never return rows (INSERT, UPDATE, etc.). A response of PGRES_EMPTY_QUERY might indicate a bug in the client software.
-- john r pierce, recycling bits in santa cruz
Thx. So it is referring to the command not a "command returning no data". ;-) On Wed, Sep 20, 2017 at 1:42 PM, John R Pierce <pierce@hogranch.com> wrote: > On 9/20/2017 10:34 AM, Igor Korot wrote: > > >From the documentation: > https://www.postgresql.org/docs/9.1/static/libpq-exec.html > > [quote] > PGRES_COMMAND_OK > > Successful completion of a command returning no data. > [/quote] > > No data = no rows, right? > > from that same page, a bit farther down, clarifying the potentially > confusing wording. > > If the result status is PGRES_TUPLES_OK, then the functions described below > can be used to retrieve the rows returned by the query. Note that a SELECT > command that happens to retrieve zero rows still shows PGRES_TUPLES_OK. > PGRES_COMMAND_OK is for commands that can never return rows (INSERT, UPDATE, > etc.). A response of PGRES_EMPTY_QUERY might indicate a bug in the client > software. > > > -- > john r pierce, recycling bits in santa cruz -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
On Wednesday, September 20, 2017 1:47:05 PM EDT Igor Korot wrote: >Thx. >So it is referring to the command not a "command returning no data". ;-) assumingcreate table t (c int); select c from t;- PQresultStatus(result) == PGRES_TUPLES_OK- PQntuples(result) == number or rows returned (int) insert into t(c)values(1);- PQresultStatus(result) ==PGRES_COMMAND_OK- PQcmdTuples(result) == "1" (note: char*) insert into t(c)values(1) returning c;- PQresultStatus(result) ==PGRES_TUPLES_OK- PQntuples(result) == 1 (int) >On Wed, Sep 20, 2017 at 1:42 PM, John R Pierce <pierce@hogranch.com> wrote: >> On 9/20/2017 10:34 AM, Igor Korot wrote: >> >From the documentation: >> https://www.postgresql.org/docs/9.1/static/libpq-exec.html >> >> [quote] >> PGRES_COMMAND_OK >> >> Successful completion of a command returning no data. >> [/quote] >> >> No data = no rows, right? >> >> from that same page, a bit farther down, clarifying the potentially >> confusing wording. >> >> If the result status is PGRES_TUPLES_OK, then the functions described below >> can be used to retrieve the rows returned by the query. Note that a SELECT >> command that happens to retrieve zero rows still shows PGRES_TUPLES_OK. >> PGRES_COMMAND_OK is for commands that can never return rows (INSERT, >> UPDATE, >> etc.). A response of PGRES_EMPTY_QUERY might indicate a bug in the client >> software.