Re: Select statement error !!!!

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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