OTL 4.0, Example 507 (Datatype override in SELECT, MS SQL Server)

This example demonstrates a SELECT statement with a numeric column, being converted into a null terminated string. It is a useful technique when there is a need to read and write numbers, which are larger than 16 digits.

Source Code

#include <iostream>
using namespace std;

#include <stdio.h>
#define OTL_ODBC_MSSQL_2005 // Compile OTL 4/ODBC, MS SQL 2005
#define OTL_FREETDS_ODBC_WORKAROUNDS // Enable the FreeTDS / ODBC workarounds for MS SQL
//#define OTL_ODBC // Compile OTL 4/ODBC. Uncomment this when used with MS SQL 7.0/ 2000
//#define OTL_ODBC_UNIX // Compile OTL 4 / ODBC. Uncomment this when used in Linux / Unix
#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(12345678900000000+convert(numeric,: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);
  o<<i<<tmp;
 }
}

void select()

 otl_stream i;

 i.set_column_type(1,otl_var_char,40); // use a string(40) instead of default double
 i.open(50, // buffer size
        "select * from test_tab "
        "where f1>=12345678900000000+convert(numeric,:f11<int>) "
        "  and f1<=12345678900000000+convert(numeric,:f12<int>)*2",
           // SELECT statement
        db // connect object
       ); 
   // create select stream
 
 char f1[40];
 char f2[31];

 i<<8<<8; // assigning :f11, :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>>f2;
  cout<<"f1="<<f1<<", f2="<<f2<<endl;
 }

 i<<4<<4; // assigning :f11, :f12 = 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 ODBC environment
 try{

  db.rlogon("scott/tiger@freetds_mssql"); // connect to ODBC

  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 numeric, 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.var_info<<endl; // print out the variable that caused the error
 }

 db.logoff(); // disconnect from ODBC

 return 0;

}

Output

f1=12345678900000008, f2=Name8
f1=12345678900000009, f2=Name9
f1=12345678900000010, f2=Name10
f1=12345678900000011, f2=Name11
f1=12345678900000012, f2=Name12
f1=12345678900000013, f2=Name13
f1=12345678900000014, f2=Name14
f1=12345678900000015, f2=Name15
f1=12345678900000016, f2=Name16
f1=12345678900000004, f2=Name4
f1=12345678900000005, f2=Name5
f1=12345678900000006, f2=Name6
f1=12345678900000007, f2=Name7
f1=12345678900000008, f2=Name8

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Copyright © 1996-2017, Sergei Kuchin, email: skuchin@gmail.com, skuchin@gmail.com/a>.

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