# OTL 4.0, Example 145
(otl_stream::describe_select() with a simple Select)

# Example 145 (otl_stream::describe_select() with a simple Select)

This example demonstrates the otl_stream::describe_select() with a simple SELECT statement.

## Source Code

    #include <iostream>
    using namespace std;

    #include <stdio.h>

    // #define OTL_ODBC_UNIX // uncomment this line if UnixODBC is used
    #if !defined(_WINDOWS_) && !defined(_WIN64)
    #define OTL_ODBC
    #else
    #define OTL_ODBC_POSTGRESQL // required with PG ODBC on Windows
    #endif
    #include <otlv4.h> // include the OTL 4.0 header file

    otl_connect db; // connect object

    void select()
    {
     otl_stream i(10, // buffer size
                  "select * from test_tab",
                     // SELECT statement
                  db // connect object
                 );
       // create select stream

     otl_column_desc* desc;
     int desc_len;

     desc=i.describe_select(desc_len);

     for(int n=0;n<desc_len;++n){
      cout<<"========== COLUMN #"<<n+1<<" ==========="<<endl;
      cout<<"name="<<desc[n].name<<endl;
      cout<<"dbtype="<<desc[n].dbtype<<endl;
      cout<<"otl_var_dbtype="<<desc[n].otl_var_dbtype<<endl;
      cout<<"dbsize="<<desc[n].dbsize<<endl;
      cout<<"scale="<<desc[n].scale<<endl;
      cout<<"prec="<<desc[n].prec<<endl;
      cout<<"nullok="<<desc[n].nullok<<endl;
     }

    }

    int main()
    {
     otl_connect::otl_initialize(); // initialize ODBC environment
     try{

       db.rlogon("UID=scott;PWD=tiger;DSN=postgresql"); // connect to ODBC
    //  db.rlogon("scott/tiger@postgresql"); // connect to ODBC, alternative format
                                        // of connect string
      otl_cursor::direct_exec
       (
        db,
        "drop table test_tab",
        otl_exception::disabled // disable OTL exceptions
       ); // drop table

       db.commit();

      otl_cursor::direct_exec
       (
        db,
        "create table test_tab(f1 int, f2 varchar(30), f3 timestamp, f4 text)"
        );  // create table

      db.commit(); // committing the create table statement to to the database

      select(); // select records from table

     }

     catch(otl_exception& p){ // intercept OTL exceptions
      cerr<<p.msg<<endl; // print out error message
      cerr<<p.stm_text<<endl; // print out SQL that caused the error
      cerr<<p.var_info<<endl; // print out the variable that caused the error
     }

     db.logoff(); // disconnect from ODBC

     return 0;

    }

## Output

    ========== COLUMN #1 ===========
    name=f1
    dbtype=4
    otl_var_dbtype=4
    dbsize=10
    scale=0
    prec=10
    nullok=1
    ========== COLUMN #2 ===========
    name=f2
    dbtype=12
    otl_var_dbtype=1
    dbsize=30
    scale=0
    prec=30
    nullok=1
    ========== COLUMN #3 ===========
    name=f3
    dbtype=93
    otl_var_dbtype=8
    dbsize=21
    scale=0
    prec=21
    nullok=1
    ========== COLUMN #4 ===========
    name=f4
    dbtype=-1
    otl_var_dbtype=9
    dbsize=8190
    scale=0
    prec=8190
    nullok=1

Examples Contents Go Home

Copyright © 1996, 2007, Sergei Kuchin, email: skuchin@ispwest.com, skuchin@gmail.com
.

Permission to use, copy, modify and redistribute this document for any purpose is hereby granted without fee, provided that the above copyright notice appear in all copies.