# OTL 4.0, Example 380 (Insert/Update/Select, DB2 CLOBs in stream mode, and std:strings)

This example demonstrates INSERT, UPDATE, and SELECT statements with the DB2 CLOB datatype in stream mode and std::strings.

## Source Code

    #include <iostream>
    #include <string>
    using namespace std;

    #include <stdio.h>

    #define OTL_DB2_CLI // Compile OTL 4.0/DB2 CLI
    #define OTL_STL // enable OTL support for STL
    #include <otlv4.h> // include the OTL 4.0 header file

    otl_connect db; // connect object

    void insert()
    // insert rows into table
    {
     string f2;
     otl_stream o; // defined an otl_stream variable
     o.set_lob_stream_mode(true); // set the "lob stream mode" flag
     o.open(1, // buffer size has to be set to 1 for operations with LOBs
            "insert into test_tab values(:f1<int>,:f2<varchar_long>) ",
                // SQL statement
            db // connect object
           );
     o.set_commit(0); // setting stream "auto-commit" to "off". It is required
                      // when LOB stream mode is used.

     otl_lob_stream lob; // LOB stream for reading/writing unlimited number
                         // of bytes regardless of the buffer size.
     for(int i=1;i<=20;++i){
      f2.erase();
      f2.append(50000,'*');
      f2 += '?';
      o<<i;
      o<<lob; // Initialize otl_lob_stream by writing it
              // into otl_stream

      lob.set_len(50001+23123); // setting the total size of
                                // the CLOB to be written.
       // It is required for bakward compatibility

      lob<<f2; // writing first chunk of the CLOB into lob

      f2.erase();
      f2.append(23122,'*');
      f2 += '?';
      lob<<f2; // writing the second chunk of the CLOB into lob
      lob.close(); // closing the otl_lob_stream
     }

     db.commit(); // committing transaction.
    }

    void update()
    // insert rows in table
    {
     string f2;
     otl_stream o; // defined an otl_stream variable
     o.set_lob_stream_mode(true); // set the "lob stream mode" flag
     o.open(1, // buffer size has to be set to 1 for operations with LOBs
            "update test_tab "
            "   set f2=:f2<varchar_long> "
            "where f1=:f1<int> ",
                // SQL statement
            db // connect object
           );
     otl_lob_stream lob;
     o.set_commit(0); // setting stream "auto-commit" to "off".
     f2.append(6000,'#');
     f2+='?';
     o<<lob; // Initialize otl_lob_stream by writing it
             // into otl_stream.
     o<<5;
     lob.set_len(6001*4); // setting the total size of of the CLOB to be written
     for(int i=1;i<=4;++i)
      lob<<f2; // writing chunks of the CLOB into the otl_lob_stream
     lob.close(); // closing the otl_lob_stream
     db.commit(); // committing transaction

    }

    void select()
    {
     string f2;
     otl_stream i; // defined an otl_stream variable
     i.set_lob_stream_mode(true); // set the "lob stream mode" flag
     i.open(1, // buffer size. To read CLOBs, it should be set to 1
            "select * from test_tab where f1>=:f11<int> and f1<=:f12<int>*2",
              // SELECT statement
            db // connect object
           );
       // create select stream

     int f1;
     otl_lob_stream lob; // Stream for reading CLOB

     lob.setStringBuffer(40000); // Set a bigger internal buffer (default is 4096 bytes)
                                 // for reading chunks of the CLOB, before each chunk
                                 // gets appended to the output string.
     i<<4<<4; // assigning :f11 = 4, :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;
      cout<<"f1="<<f1;
      i>>lob; // initializing CLOB stream by reading the CLOB reference
              // into the otl_lob_stream from the otl_stream.
      lob>>f2;
      cout<<", f2="<<f2[0]<<f2[f2.length()-1]<<", len="<<(int)f2.length()<<endl;
      lob.close(); // closing the otl_lob_stream. This step may be skipped.

     }

    }

    int main()
    {
     otl_connect::otl_initialize(); // initialize the database API 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 clob(1M))"
        );  // create table

      insert(); // insert records into table
      update(); // update records in 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=4, f2=*?, len=73124
    f1=5, f2=#?, len=24004
    f1=6, f2=*?, len=73124
    f1=7, f2=*?, len=73124
    f1=8, f2=*?, len=73124

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

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