Listing 2: Function CColumns::MakeColumnListFromQuery

BOOL CColumns::MakeColumnListFromQuery()
{
   BOOL       bRtn=FALSE; // Assume we'll fail; allow reselect
   RETCODE    rc;         // Return code from ODBC functions
   CColumnInfo*   pColInfo;   // Data type output for each column
   int        index;      // Index for columns
   short      iCols;      // the number of columns in this query
   HSTMT      hStmt;      // allocated and used in this function


   // check if this object was constructed sans open CDatabase
   if ( (m_hstmt == SQL_NULL_HSTMT) || (!m_pDatabase->IsOpen()) )
        ThrowDBException(SQL_INVALID_HANDLE); 
        //  <<--< it was, so toss cookies...
    
   // safe to continue, so create a meta-data only query
   ReplaceWhereClause();
    
   // Get a HSTMT for use in this function
   rc = ::SQLAllocStmt( m_pDatabase->m_hdbc, &hStmt );
   if (SQL_NOTSUCCESSFUL(rc))
   {
      DecodeSQLError(rc, m_pDatabase->m_hdbc, hStmt, THIS_FILE, __LINE__);
      goto cleanup;
   }

   // Execute the query and retrieve the results
   rc = ::SQLExecDirect(hStmt, 
            (unsigned char*)
            m_QueryNoWhere.GetBuffer(m_QueryNoWhere.GetLength()), 
            m_QueryNoWhere.GetLength());
   if(SQL_NOTSUCCESSFUL(rc)) 
   {
       DecodeSQLError(rc, m_pDatabase->m_hdbc, hStmt,
                      THIS_FILE, __LINE__);
       m_QueryNoWhere.ReleaseBuffer();
       goto cleanup;
    }
    m_QueryNoWhere.ReleaseBuffer();
    
   // how many columns are there in this select?
   rc = ::SQLNumResultCols( hStmt, &iCols);
   if(SQL_NOTSUCCESSFUL(rc)) 
   {
       DecodeSQLError(rc, m_pDatabase->m_hdbc, hStmt, THIS_FILE, __LINE__);
       goto cleanup;
   }
    
    // make the CPtrArray large enough to hold all of the
    // CColumnInfo *'s
    // m_ColumnList.SetSize(iCols);

   // now loop through the column set gathering facts about each one
   // to store in a CColumnInfo class for each column. All the
   // CColumnInfo classes will be added to the m_ColumnList 
   for(index = 0;  index < iCols;  index++) 
   {
       pColInfo = new CColumnInfo;
       if (pColInfo == NULL)
           goto cleanup;      
       pColInfo->nColInRslt = index +1;

       // get the SQL_xxx type (and related info) for the column
       rc = ::SQLDescribeCol(hStmt,
                            (UWORD)(index + 1), 
                             NULL, 
                             0, 
                             NULL,
                             &pColInfo->fSqlType,
                             &pColInfo->cbPrecision,
                             &pColInfo->ibScale,
                             &pColInfo->fNullable);
       if(SQL_NOTSUCCESSFUL(rc))
       {
          DecodeSQLError(rc, m_pDatabase->m_hdbc, hStmt, THIS_FILE, __LINE__);
          goto cleanup;
       }
                
       // Get the named type of the column for mapping
       //
       rc = ::SQLColAttributes(hStmt,
                              (UWORD)(index + 1),
                              SQL_COLUMN_TYPE_NAME,           
                              &pColInfo->szNamedType,
                              sizeof(pColInfo->szNamedType),
                              NULL,
                              NULL);
       if(SQL_NOTSUCCESSFUL(rc))
       {
          DecodeSQLError(rc, m_pDatabase->m_hdbc, hStmt, THIS_FILE, __LINE__);
          goto cleanup;


       }
                
       // Get the display size in case this column gets converted to char
       //
       rc = ::SQLColAttributes(hStmt,
                              (UWORD)(index + 1),
                              SQL_COLUMN_DISPLAY_SIZE,
                              NULL,
                              sizeof(pColInfo->cbDspSize),
                              NULL,
                              &pColInfo->cbDspSize);
       if(SQL_NOTSUCCESSFUL(rc))
       {
          DecodeSQLError(rc, m_pDatabase->m_hdbc, hStmt, THIS_FILE, __LINE__);
          goto cleanup;
       }

       // Get the name of this column
       //
       rc = ::SQLColAttributes(hStmt,
                              (UWORD)(index + 1),
                              SQL_COLUMN_NAME,
                              &pColInfo->szColumnName,
                              sizeof(pColInfo->szColumnName),
                              NULL,
                              NULL);

       if(SQL_NOTSUCCESSFUL(rc))
       {
          DecodeSQLError(rc, m_pDatabase->m_hdbc, hStmt, THIS_FILE, __LINE__);
          goto cleanup;
       }
                
       // Get the name of the table containing this column
       //
       rc = ::SQLColAttributes(hStmt,
                              (UWORD)(index + 1),
                              SQL_COLUMN_TABLE_NAME,
                              &pColInfo->szFromTable,
                              sizeof(pColInfo->szFromTable),
                              NULL,
                              NULL);

       if(SQL_NOTSUCCESSFUL(rc))
       {
          DecodeSQLError(rc, m_pDatabase->m_hdbc, hStmt, THIS_FILE, __LINE__);
          goto cleanup;
       }
                
       // now that we have all the info we need on this column
       // finish up by allocating storage for this column's local
       // member variable and adding the finished CColumnInfo to
       // the column list
       if ( ! AllocStorageForColumnVar(pColInfo) )
              goto cleanup;
       
       if ( !(MapColumnSQLTypeToCType(pColInfo)) 
         || !(GetCreateParamCount(pColInfo))     )
              goto cleanup;

       AddColumnInfoToList(pColInfo);                
   }
   // if we get here, all went well
   if ( GenerateTableCreationString() )
        bRtn = TRUE;
   // Clean up the statement handle
   //
cleanup:
    SQLFreeStmt(hStmt, SQL_CLOSE);
    SQLFreeStmt(hStmt, SQL_UNBIND);    
    return bRtn;
}
//End of File