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 is
// not up to the ODBC 3.5 level just yet

// #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
{
// open a stream with no implicit committing
 otl_nocommit_stream o
(50, // buffer size
    "insert into test_tab values(:f1<float>,:f2<char[31]>)", 
        // SQL statement
    db // connect object
    );
 char tmp[32];

otl_cursor::direct_exec(db,"BEGIN TRANSACTION");
// begin transaction. This explicit construct needs to be used
// because the ODBC driver could eventually run into the
// "Function Sequence Error" error.

 for(int i=1;i<=100;++i){
  sprintf(tmp,"Name%d",i);
  if(i==10)
   o<<(float)i<<otl_null();
  else
   o<<(float)i<<tmp;
 }
o.flush(); // flush the stream buffer to make sure that
// all rows get to the table
otl_cursor::direct_exec(db,"COMMIT TRANSACTION");
// commit transaction

}

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",1);
// connect to the database and set the auto-commit to on.
// The auto-commit is needed to make "BEGIN TRANSACTION" /
// "COMMIT TRANSACTION" work properly.


  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=NULL
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, 2006, Sergei Kuchin, email: skuchin@gmail.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. THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.