# OTL 4.0, Example 208 (otl_lob_stream and SELECT INTO FOR UPDATE, Oracle)

# Example 208 (otl_lob_stream and SELECT INTO FOR UPDATE, Oracle)

This example demonstrates INSERT, SELECT INTO FOR UPDATE, and SELECT statements with the Oracle 8,8i,9i CLOB datatype in the stream mode. The example is similar to example 56, and provided only as part of the package of examples to demonstrate the extended otl_lob_stream class.

## Source Code

    #include <iostream>
    using namespace std;

    #include <stdio.h>

    //#define OTL_ORA8 // Compile OTL 4.0/OCI8
    #define OTL_ORA8I // Compile OTL 4.0/OCI8i
    //#define OTL_ORA9I // Compile OTL 4.0/OCI9i
    #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(6000); // 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(),empty_clob()) "
                  "returning f2, f3 into :f2<clob>,:f3<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.

     int i,j;
     otl_lob_stream lob; // LOB stream for reading/writing unlimited number
                         // of bytes regardless of the buffer size.
     otl_lob_stream lob2; // LOB stream for reading/writing unlimited number
                         // of bytes regardless of the buffer size.

     for(i=1;i<=20;++i){
      o<<i;
      o<<lob; // Initialize otl_lob_stream by writing it
              // into otl_stream.
      o<<lob2; // Initialize otl_lob_stream by writing it
              // into otl_stream.

      for(j=0;j<5000;++j)
       f2[j]='*';
      f2[5000]='?';
      f2.set_len(5001);

      lob.set_len(5001+2123); // setting the total  size of
                              // the CLOB to be written.

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

      f2[2122]='?';
      f2.set_len(2123); // setting the size of the second chunk

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

      for(j=0;j<5000;++j)
       f2[j]='*';
      f2[5000]='?';
      f2.set_len(5001);
      lob2.set_len(5001+2123); // setting the total  size of
                              // the CLOB to be written.

      lob2<<f2; // writing first chunk of the CLOB into lob

      f2[2122]='?';
      f2.set_len(2123); // setting the size of the second chunk

      lob2<<f2; // writing the second chunk of the CLOB into lob
      lob2.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
                  "begin "
                  "  select f2 into :f2<clob,in> "
                  "  from test_tab "
                  "  where f1=:f1<int,in> "
                  "  for update; "
                  "end;",
                     // 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<<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()
    {
     otl_long_string f2(3000); // 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>=: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
     otl_lob_stream lob2; // Stream for reading CLOB

     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<<endl;
      i>>lob; // initializing CLOB stream by reading the CLOB reference
              // into the otl_lob_stream from the otl_stream.
      i>>lob2; // 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.
      n=0;
      while(!lob2.eof()){ // read while not "end-of-file" -- end of CLOB
       ++n;
       lob2>>f2; // reading a chunk of CLOB
       cout<<"   chunk #"<<n;
       cout<<", f3="<<f2[0]<<f2[f2.len()-1]<<", len="<<f2.len()<<endl;
      }
      lob2.close(); // closing the otl_lob_stream.

     }

    }

    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, f3 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=3000
       chunk #2, f2=**, len=3000
       chunk #3, f2=*?, len=1124
       chunk #1, f3=**, len=3000
       chunk #2, f3=**, len=3000
       chunk #3, f3=*?, len=1124
    f1=5
       chunk #1, f2=##, len=3000
       chunk #2, f2=##, len=3000
       chunk #3, f2=?#, len=3000
       chunk #4, f2=##, len=3000
       chunk #5, f2=##, len=3000
       chunk #6, f2=##, len=3000
       chunk #7, f2=##, len=3000
       chunk #8, f2=##, len=3000
       chunk #9, f2=#?, len=4
       chunk #1, f3=**, len=3000
       chunk #2, f3=**, len=3000
       chunk #3, f3=*?, len=1124
    f1=6
       chunk #1, f2=**, len=3000
       chunk #2, f2=**, len=3000
       chunk #3, f2=*?, len=1124
       chunk #1, f3=**, len=3000
       chunk #2, f3=**, len=3000

       chunk #3, f3=*?, len=1124
    f1=7
       chunk #1, f2=**, len=3000
       chunk #2, f2=**, len=3000
       chunk #3, f2=*?, len=1124
       chunk #1, f3=**, len=3000
       chunk #2, f3=**, len=3000
       chunk #3, f3=*?, len=1124
    f1=8
       chunk #1, f2=**, len=3000
       chunk #2, f2=**, len=3000
       chunk #3, f2=*?, len=1124
       chunk #1, f3=**, len=3000
       chunk #2, f3=**, len=3000
       chunk #3, f3=*?, len=1124

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