Subject: Re: Select statement error !!!!
From: Oliver Elphick <olly@lfix.co.uk>
To: Vutharkar Goutham <goutham4u@hotmail.com>
Cc: pgsql-docs@postgresql.org
In-Reply-To: <Sea1-F145GKvt87AM7t0001f343@hotmail.com>
References: <Sea1-F145GKvt87AM7t0001f343@hotmail.com>
Content-Type: text/plain
Organization: LFIX Limited
Message-Id: <1064423595.6609.370.camel@linda.lfix.co.uk>
Mime-Version: 1.0
Date: Wed, 24 Sep 2003 18:13:16 +0100
Content-Transfer-Encoding: 7bit

On Wed, 2003-09-24 at 15:48, Vutharkar Goutham wrote:
...
> So we are using PostgreSQL as our database to store the captured data from a 
> LAN or from outside network. So in the mean process we successfully captured 
> the data packets and sent them into the database tables but the problem is 
> when we are are trying to retrieve data then we are failing and we dont know 
> how to proceed further. We searched all the forums for right answer but 
> didn't get to it so i was forced to post here. Now let me paste the code 
> here ....
> 
> 
> 
> 
> #include<stdio.h>
> #include<libpq-fe.h>
> 
> void exit_nicely(PGconn *conn)
> {
> PQfinish(conn);
> exit(1);
> }
> 
> int main()
> {
> char *pghost,*pgport,*pgoptions,*pgtty;
> char *dbname;
> char query[1024];
> struct PQprintOpt *po;
> int nFields;
> int i,j;
> FILE *fp;
> 
> fp = fopen("data.txt","w+");
> 
> strcpy(query,"select * from UDP_Table");
                              ^^^^^^^^^
If this table's name is truly mixed case, it must be enclosed in double
quotes; otherwise it will be folded to lowercase automatically.

> printf("\nInitial Query is : %s\n",query);
> PGconn *conn;
> PGresult *res;
> 
> pghost = NULL;
> pgport = NULL;
> pgoptions = NULL;
> pgtty = NULL;
> dbname = "Project";
> 
> conn = PQsetdb(pghost,pgport,pgoptions,pgtty,dbname);
> 
> if(PQstatus(conn) == CONNECTION_BAD)
> {
> fprintf(stderr,"Failed to make a connection.\n",dbname);
> fprintf(stderr,"%s",PQerrorMessage(conn));
> exit_nicely(conn);
> }
> else
> printf("\nConnection established with backend.\n");
> 
> res = PQexec(conn,"BEGIN");
> 
> if(!res || PQresultStatus(res)!=PGRES_TUPLES_OK)
                                  ^^^^^^^^^^^^^^^
                                  PGRES_COMMAND_OK
> {
> fprintf(stderr,"Begin Failed.\n");
> PQclear(res);
> exit_nicely(conn);
> }
> else
> printf("\nBegin Transaction Completed Successfully.\n");
> 
> printf("\nQuery B4 execution is : %s\n",query);
> 
> res = PQexec(conn,query);
> 
> if(!res || PQresultStatus(res)!=PGRES_COMMAND_OK)
                                  ^^^^^^^^^^^^^^^^
                                  PGRES_TUPLES_OK

> {
> fprintf(stderr,"\nSelect Statement Failed.\n");
> PQclear(res);
> exit_nicely(conn);
> }
> else
> {
> printf("\nSelect statement executed successfully.\n");
> PQprint(fp,res,(const struct PQprintOpt *)po);

segfaults here - the third parameter should be const PQprintopt * which
should point to a PQprintOpt struct with values assigned (see the libpq
manual).

> }
> 
> // Print Attribute Names
> 
> printf("\nThe Attribute Names are \n\n");
> 
> nFields = PQnfields(res);
> 
> for(i = 0;i<nFields;i++)
> printf("%-15s",PQfname(res,i));
> printf("\n\n");
> 
> //Print out rows
> 
> printf("The Rows in the table are \n\n");
> 
> for(i = 0;i<PQntuples(res);i++)
> {
> for(i = 0;j<nFields;j++)
     ^^^
      j

> printf("%-15s",PQgetvalue(res,i,j));
> printf("\n");
> }
> 
> res = PQexec(conn,"COMMIT");
> 
> PQclear(res);
> 
> PQfinish(conn);
> 
> return 0;
> }
> 
> 
> I tried as told by you but still i failed. So please dont mind solving the 
> problem for me if i am not troubling you. Your help will be appreciated a 
> lot by our project team.
> 
> Thank You,
> 
> Goutham.V
> MSIT.
> 
> _________________________________________________________________
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-- 
Oliver Elphick                                Oliver.Elphick@lfix.co.uk
Isle of Wight, UK                             http://www.lfix.co.uk/oliver
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      them that love God, to them who are the called  
      according to his purpose."            
                                   Romans 8:28