# OTL 4.0, Example 283 (otl_stream and NULLs)

# Example 283 (otl_stream and NULLs)

This example demonstrates the otl_stream with NULLs.

## Source Code

    #include <iostream>
    using namespace std;

    #include <stdio.h>

    #define OTL_ODBC // Compile OTL 4.0/ODBC
    #define ODBCVER 0x0250 // ODBC Version # needs to be downgraded
                           // to 2.5 because the SQLite ODBC driver seems
                           // to run slower when ODBC 3.x functions
                           // used (performance is not as good as with
                           // ODBC 2.5 function calls)
    // #define OTL_ODBC_UNIX // uncomment this line if UnixODBC is used
    #include <otlv4.h> // include the OTL 4.0 header file

    otl_connect db; // connect object

    void insert()
    // insert rows into table
    {
     otl_stream o
       (50, // buffer size
        "insert into test_tab values(:f1<int>,:f2<char[31]>)",
            // SQL statement
         db // connect object
        );
     char tmp[32];

     for(int i=1;i<=100;++i){
      sprintf(tmp,"Name%d",i);
      if(i==10)
       o<<i<<otl_null();
      else
       o<<i<<tmp;
     }
    }

    void select()
    {
     otl_stream i(50, // buffer size
                  "select * from test_tab where f1>=:f11<int> and f1<=:f12<int>*2",
                     // SELECT statement
                  db // connect object
                 );
       // create select stream

     float f1;
     char f2[31];

     i<<8<<8; // assigning :f11 = 8, :f12=8
       // SELECT automatically executes when all input variables are
       // assigned. First portion of output rows is fetched to the buffer

     while(!i.eof()){ // while not end-of-data
      i>>f1;
      if(i.is_null())
       cout<<"f1=NULL,";
      else
       cout<<"f1="<<f1<<",";
      i>>f2;
      if(i.is_null())
       cout<<"f2=NULL";
      else
       cout<<"f2="<<f2;
      cout<<endl;
     }

    }

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

      db.rlogon("scott/tiger@sqlite");

      otl_cursor::direct_exec
       (
        db,
        "drop table test_tab",
        otl_exception::disabled // disable OTL exceptions
       ); // drop table

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

      insert(); // insert records into table
      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.sqlstate<<endl; // print out SQLSTATE message
      cerr<<p.var_info<<endl; // print out the variable that caused the error
     }

     db.logoff(); // disconnect from ODBC

     return 0;

    }

## Output

    f1=8, f2=Name8
    f1=9, f2=Name9
    f1=10, f2=  -- f2 is supposed to be NULL. Seems similar to this bug.
    f1=11, f2=Name11
    f1=12, f2=Name12
    f1=13, f2=Name13
    f1=14, f2=Name14
    f1=15, f2=Name15
    f1=16, f2=Name16

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

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