OTL 4.0, Example 740 (Stored procedure with output parameter)

This example demonstrates a MySQL stored procedure that inserts a new row into a table and returns an auto-incremented primary key value as an output parameter. MySQL ODBC driver doesn't seem to support output parameters in stored procedures. The technique that this code example demonstrates can be used as a workaround for reading output parameters out of stored procedures.

Source Code

#include <iostream>
using namespace std;

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define OTL_ODBC // Compile OTL 4.0/ODBC
// The following #define is required with MyODBC 3.51.11 and higher
#define OTL_ODBC_SELECT_STM_EXECUTE_BEFORE_DESCRIBE
// #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 and read database generated / auto-incremented 
// key values by calling a stored procedure that has 
// an output parameter
{ 
  otl_stream o(1, // buffer size
               "{call prc_1(@f1_1,:f2_2<char[31],in>)}",
               db
              );
  o.set_commit(0); // set stream auto-commit to OFF
  char f2_in[32];
  int f1_out;

  // stream to read the value of the output parameter
  otl_stream s(1, "select @f1_1  :#1<int>", db, otl_implicit_select);

  for(int i=1;i<=10;++i) {
#if defined(_MSC_VER)
#if (_MSC_VER >= 1400) // VC++ 8.0 or higher
    sprintf_s(f2_in,sizeof(f2_in),"Name%d",i);
#else
    sprintf(f2_in,"Name%d",i);
#endif
#else
    sprintf(f2_in,"Name%d",i);
#endif
    o<<f2_in; // write input variable :f2

    s.rewind();
    while(!s.eof()){ // while not end-of-data
      s>>f1_out;
      cout<<"f1="<<f1_out<<", f2="<<f2_in<<endl;
    }
  }
  db.commit(); // commit transaction
 }

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

  db.rlogon("UID=scott;PWD=tiger;DSN=mysql35"); // connect to ODBC
//  db.rlogon("scott/tiger@mysql35"); // connect to ODBC, alternative format
                                    // of connect string 

    db.direct_exec
      ("drop table test_tab",
       otl_exception::disabled // disable OTL exceptions
      ); // drop table
    
    db.direct_exec
      ("CREATE TABLE test_tab "
       "(f1 INTEGER NOT NULL AUTO_INCREMENT, "
       " f2 VARCHAR(30),PRIMARY KEY (f1))"
      );  // create table

    db.direct_exec
      ("drop procedure prc_1",
       otl_exception::disabled // disable OTL exceptions
      ); // drop table

    db<<
      "create procedure prc_1 "
      " (out f11 int, "
      " in f22 varchar(30)) "
      "begin "
      " insert into test_tab(f2) values(f22); "
      " select last_insert_id() into f11; "
      " end; ";
    
    insert(); // insert records into 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=1, f2=Name1
f1=2, f2=Name2
f1=3, f2=Name3
f1=4, f2=Name4
f1=5, f2=Name5
f1=6, f2=Name6
f1=7, f2=Name7
f1=8, f2=Name8
f1=9, f2=Name9
f1=10, f2=Name10

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