Delete with PQexec by given ID in C++

Question

I am taking ID from my user and then i want to delete that ID from the database. I am using postgresql. but the query is not running. When i give hard code value like id=5 then it runs but when i give it user's value like id = DeleteId then it doesn't run. Here is the function:

void DeleteValue(PGconn *conn, int DeleteId)
      {

       PGresult *res = PQexec(conn, "DELETE FROM testData where ID =  DeleteId" );

         if (PQresultStatus(res) != PGRES_COMMAND_OK)
         {
           cout << "Delete testData record failed." << endl;
           PQclear(res);
           CloseConn(conn);
         } 
          cout << "\nDelete testData record - OK\n";
          PQclear(res);
      }

Doesn't look to me like you are passing `DeleteId` to your query. You need to concatenate your query string with id: http://stackoverflow.com/questions/191757/how-to-concatenate-a-stdstring-and-an-int or use prepared statement. — Łukasz Kamiński, Apr 11 '17 at 09:25
Do you mean this? DELETE FROM testData where ID = DeleteId.c_str() — Muhammad Mubeen, Apr 11 '17 at 09:43
Also tried this one: PGresult *res = PQexec(conn, "DELETE FROM testData where ID = " + DeleteId.c_str() ); — Muhammad Mubeen, Apr 11 '17 at 09:44
`"DELETE FROM testData where ID = " + std::to_string(DeleteId)` — Łukasz Kamiński, Apr 11 '17 at 09:49
Its showing error on this too: cannot convert ‘std::basic_string’ to ‘const char*’ for argument ‘2’ to ‘PGresult* PQexec(PGconn*, const char*)’ — Muhammad Mubeen, Apr 11 '17 at 09:51

score 0 · Accepted Answer · answered Apr 11 '17 at 11:50

0

Just solved my own problem.first concatenate it with the help of sprintf and then execute the query. Here is the solution of the problem

sprintf(sql,"DELETE FROM testData WHERE id = %d",DeleteId);
PGresult *res = PQexec(conn, sql );

answered Apr 11 '17 at 11:50

Muhammad Mubeen

11
3

Delete with PQexec by given ID in C++

1 Answers1