Обсуждение: PQgetvalue failed to get non-text data under binary format
Hi, I am new to PostgreSQL and tried using the libpq C library. I can read a test table using PQgetvalue for text format, i.e. format = 0. However, when I experiment with using binary output format, I was unable to read anything else except result set fiend that is in char(x), varchar(x), i.e., character string data. What have I done wrong? int * pId; LPSTR pszName; double * pSalary; PGresult *pResult = PQexecParams(m_pConn, (LPCTSTR)strSelect, nParams, parmTypes, paramValues, parmLengths,parmFormats, 1); pId = (int *)PQgetvalue(pResult, row, 0); pszName = (LPSTR)PQgetvalue(pResult, row, 1); pSalary = (double *)PQgetvalue(pResult,row, 6); printf("id: %d name: %s salary: %f", *pId, pszName, *pSalary); What I got is as follow: + + + printing resultset, 2 rows, 8 columns id: 167772160 name: Amy Who salary: 0.000000 id: 16777216 name: David Smith salary: 0.000000 Which supposed to return: id: 10 name: Amy Who salary: 150000.00 id: 1 name: David Smith salary: 350000.00 Any help is greatly appreciated! Jeff
On Mon, May 21, 2007 at 12:33:28AM -0400, Y. Ming Lam wrote: > I am new to PostgreSQL and tried using the libpq C library. I can read > a test table using PQgetvalue for text format, i.e. format = 0. > However, when I experiment with using binary output format, I was unable > to read anything else except result set fiend that is in char(x), > varchar(x), i.e., character string data. [...] > What I got is as follow: > > + + + printing resultset, 2 rows, 8 columns > id: 167772160 name: Amy Who salary: 0.000000 > id: 16777216 name: David Smith salary: 0.000000 > > Which supposed to return: > id: 10 name: Amy Who salary: 150000.00 > id: 1 name: David Smith salary: 350000.00 For numeric types you'll need to convert binary values from network byte order to host byte order (e.g., using ntohl() for 32-bit values). Notice that 167772160 = 0x0a000000 and 16777216 = 0x01000000, which are the values you're expecting except for the reversed byte order. -- Michael Fuhr