# OTL 4.0, Example 385 (Insert/Update/Select with Oracle 8i/9i/10g CLOB in stream mode and otl_long_string::set_last_piece())

This example demonstrates INSERT, UPDATE, and SELECT statements with the Oracle 8 CLOB datatype in stream mode and otl_long_string::set_last_piece().

## Source Code

    #include <iostream>
    using namespace std;

    #include <stdio.h>

    #define OTL_ORA8I // Compile OTL 4.0/OCI8i
    //#define OTL_ORA9I // Compile OTL 4.0/OCI9i
    //#define OTL_ORA10G // Compile OTL 4.0/OCI10g
    //#define OTL_ORA10G_R2 // Compile OTL 4.0/OCI10gR2
    #include <otlv4.h> // include the OTL 4.0 header file

    otl_connect db; // connect object

    void insert()
    // insert rows into table
    {otl_long_string f2(60000); // define long string variable
     otl_stream o(1, // buffer size has to be set to 1 for operations with LOBs
                  "insert into test_tab values(:f1<int>,empty_clob()) "
                  "returning f2 into :f2<clob> ",
                     // 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){
      for(int j=0;j<50000;++j)
       f2[j]='*';
      f2[50000]='?';
      f2.set_len(50001);

      o<<i;

      o<<lob; // Initialize otl_lob_stream by writing it
              // into otl_stream. Weird, isn't it?

    // OTL 4.0.138 and higher does not require the LOB's total length to be
    // set beforehand. Instead, otl_long_string::last_piece can be used.
    // lob.set_len(50001+23123); // setting the total  size of
    //                            // the CLOB to be written.
    //   // It is required for compatibility
    //   // with earlier releases of OCI8: OCI8.0.3, OCI8.0.4.

      f2.set_last_piece(false);
      lob<<f2; // writing first chunk of the CLOB into lob

      f2[23122]='?';
      f2.set_len(23123); // setting the size of the second chunk

      f2.set_last_piece(true);
      lob<<f2; // writing the second (last) chunk of the CLOB into lob
      lob.close(); // closing the otl_lob_stream
     }

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

    void update()
    // insert rows in table
    {

     otl_long_string f2(6200); // define long string variable

     otl_stream o(1, // buffer size has to be set to 1 for operations with LOBs
                  "update test_tab "
                  "   set f2=empty_clob() "
                  "where f1=:f1<int> "
                  "returning f2 into :f2<clob> ",
                     // SQL statement
                  db // connect object
                 );

      otl_lob_stream lob;

      o.set_commit(0); // setting stream "auto-commit" to "off".

     for(int j=0;j<6000;++j){
      f2[j]='#';
     }

     f2[6000]='?';
     f2.set_len(6001);

     o<<5;
     o<<lob; // Initialize otl_lob_stream by writing it
             // into otl_stream.

    // OTL 4.0.138 and higher does not require the LOB's total length to be
    // set beforehand. Instead, otl_long_string::last_piece can be used.
    // lob.set_len(6001*4); // setting the total size of of the CLOB to be written

     for(int i=1;i<=4;++i){
      f2.set_last_piece(i==4);
      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()
    {
     otl_long_string f2(20000); // define long string variable

     otl_stream i(10, // buffer size. To read CLOBs, it can be set to a size greater than 1
                  "select * from test_tab where f1>=:f<int> and f1<=:f*2",
                     // SELECT statement
                  db // connect object
                 );
       // create select stream

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

     i<<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;
      cout<<"f1="<<f1<<endl;
      i>>lob; // initializing CLOB stream by reading the CLOB reference
              // into the otl_lob_stream from the otl_stream.
      int n=0;
      while(!lob.eof()){ // read while not "end-of-file" -- end of CLOB
       ++n;
       lob>>f2; // reading a chunk of CLOB
       cout<<"   chunk #"<<n;
       cout<<", f2="<<f2[0]<<f2[f2.len()-1]<<", len="<<f2.len()<<endl;
      }
      lob.close(); // closing the otl_lob_stream. This step may be skipped.

     }

    }

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

      db.rlogon("scott/tiger"); // connect to Oracle

      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 number, f2 clob)"
        );  // 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 Oracle

     return 0;

    }

## Output

    f1=4
       chunk #1, f2=**, len=20000
       chunk #2, f2=**, len=20000
       chunk #3, f2=**, len=20000
       chunk #4, f2=*?, len=13124
    f1=5
       chunk #1, f2=##, len=20000
       chunk #2, f2=#?, len=4004
    f1=6
       chunk #1, f2=**, len=20000
       chunk #2, f2=**, len=20000
       chunk #3, f2=**, len=20000
       chunk #4, f2=*?, len=13124
    f1=7
       chunk #1, f2=**, len=20000
       chunk #2, f2=**, len=20000
       chunk #3, f2=**, len=20000
       chunk #4, f2=*?, len=13124
    f1=8
       chunk #1, f2=**, len=20000
       chunk #2, f2=**, len=20000
       chunk #3, f2=**, len=20000
       chunk #4, f2=*?, len=13124

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