Request for help on retrieving binary data from bytea column using ODBC calls

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От Ganesh Borse
Тема Request for help on retrieving binary data from bytea column using ODBC calls
Дата
Msg-id CAEhYC0HOec=cZQG6C3HWAWNGR8R-dhrdtQwH2xBhdW8AuHG1XA@mail.gmail.com
обсуждение исходный текст
Ответы Re: Request for help on retrieving binary data from bytea column using ODBC calls  (Hiroshi Inoue <inoue@tpf.co.jp>)
Список pgsql-odbc
Dear All,

I've a VC++ application which displays the various binary files (like jpgs, xls, zips) stored in PostgrelSQL DB in bytea column.
Files are inserted into bytea column using hex encoding.

But, when I try to access this column by executing the query "select * from tablename;" from ODBC on Windows in this application, the buffer contains the same hex encoded data, but not the binary data.

Application does the following steps to retrieve this binary data. This same code works well with other DBS, like Oracle, Sybase, DB2, MSSQL & so on.
//---------------------------------------------------------------------------------------------------
// prepare query:
wchar_t *query = _T("select * from mytable;");
   SQLRETURN ret = SQLPrepare(stmt, query, SQL_NTS);
   if (!SQL_SUCCEEDED(ret))
   {
      TRACE("SybAse:SQLprepare failed.");
      DbException::sqlErrorInfo(SQL_HANDLE_STMT, stmt);
      throw DbException(std::string(""));
   }
// bind to column:
   SQLBindCol(stmtHdl, columnNumber, SQL_C_BINARY,
             m_colValue[0], m_len, &m_LenInd[0]);
// Execute query:
ret = SQLExecute(stmt);
// fetch rows
if (SQL_SUCCESS == ret || SQL_SUCCESS_WITH_INFO == ret)
{
   do {
      ret = SQLFetchScroll(m_stmt, SQL_FETCH_NEXT, 0);
      // handle data per row here...
   } while(SQL_SUCCEEDED(ret));
}
//---------------------------------------------------------------------------------------------------
Can you please help me know, how can I retrieve the data stored in bytea columns in binary format, so that those file can be handled appropriately?

Thanks in advance for your help and guidance.

Best Regards,
Ganesh

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