OTL 4.0, Example 771 (OTL stream, std::variant<>, std::tuple<>, std::array<char,...>, and span<>)

This example demonstrates how to use OTL with various standard C++ templates.

Source Code

#include <iostream>
using namespace std;

#include <stdio.h>

#define OTL_DB2_CLI // Compile OTL 4.0/DB2 CLI
#define OTL_STREAM_WITH_STD_TUPLE_ON
#define OTL_STREAM_WITH_STD_VARIANT_ON
#define OTL_STREAM_WITH_CHAR_ARRAY_ON
#if !defined(OTL_CPP_17_ON)
#define OTL_CPP_17_ON
#endif

#if defined(OTL_CPP_20_ON)
// enable OTL support for std::span
#define OTL_STREAM_WITH_STD_SPAN_ON
#endif

#include <otlv4.h> // include the OTL 4 header file

otl_connect db; // connect object

using Variant=std::variant<int,float>;
using Tuple=std::tuple<Variant,std:array<char,32>>;

#if defined(OTL_CPP_20_ON)
using Span=std::span<Tuple>;
#endif


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

 for(int i=1;i<=100;++i){
#if defined(_MSC_VER) && (_MSC_VER >= 1400) // VC++ 8.0 or higher
   sprintf_s(std::get<1>(t).data(),std::get<1>(t).size(),"Name%d",i);
#else
   sprintf(std::get<1>(t).data(),"Name%d",i);
#endif
  std::get<0>(t)=i;
#if defined(OTL_CPP_20_ON)
  o<<Span(&t,1);
#else
  o<<t;
#endif
 }

}

void select()
{ 
 otl_stream i(50, // buffer size
              "select * from test_tab where f1>=:f1_1<int> and f1<=:f1_2<int>*2",
                 // SELECT statement
              db // connect object
             ); 
   // create select stream
 
 Tuple t;
 int f1;
 char f2[32];

 i<<8<<8;

// C++11 range-for loop can be used with OTL streams
 for(auto& it : i){
   it>>t;
   const Variant& v=std::get<0>(t);
   cout<<"f1="<<std::get<0>(v)<<", f2="<<std::get<1>(t).data()<<endl;
 }

 i<<4<<4; // assigning :f = 4
   // 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>>f2;
  cout<<"f1="<<f1<<", f2="<<f2<<endl;
 }


}

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

  db.rlogon("scott/tiger@db2sql"); // connect to the database

  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(31))"
    );  // 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.var_info<<endl; // print out the variable that caused the error
 }

 db.logoff(); // disconnect from the database

 return 0;

}

Output

f1=8, f2=Name8
f1=9, f2=Name9
f1=10, f2=Name10
f1=11, f2=Name11
f1=12, f2=Name12
f1=13, f2=Name13
f1=14, f2=Name14
f1=15, f2=Name15
f1=16, f2=Name16
f1=4, f2=Name4
f1=5, f2=Name5
f1=6, f2=Name6
f1=7, f2=Name7
f1=8, f2=Name8

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