Creating table with null and not null values.

I have to create a table with 5 Null nd 5 Not Null fields.My questionis which fields are place first?Not or Not Null and why???

What you mean is: the person who asked you the question thought the order of columns was important, and wanted to see if you agreed. Or maybe they were just asking the question to see whether you thought it was important (as a test of your understanding of the database).
When I started out in Oracle I was told that it was good practice to have the mandatory columns first and then the optional columns. But if you do some research you find this: the impact of column ordering on space management is: empty nullable columns at the end of the table take up zero bytes whereas empty nullable columns at the middle of the table take up one byte each. I think if that saving really is important to you you need to spring for an additional hard drive.
Besides, even if you do organise your columns as you suggest, what happens when you add an eleventh NOT NULL column to your table? It gets tacked on to the end of your table. Your whole neat organisation is blown.
What does still matter is the positioning of large VARCHAR2 columns: they should be the last columns on your table in case they create chaining. Then any query that doesn't need the large columns can be satisfied without reading the chained block, something that can't be guaranteed if you've got columns after a VARCHAR2(4000) column. This doesn't apply to CLOBs, etc. which are stored separately anyway.
Cheers, APC

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    There is some progress. Communication from a former Microsoft employee tells us this:
    Shivendra Vishal
    Engineer at Microsoft
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    ExceptionFlags: 00000000
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    Parameter[0]: 0000000000000000
    Parameter[1]: 0000000000000000
    Attempt to read from address 0000000000000000
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    r11=00000000106fcd20 r12=0000000000000000 r13=0000000000000002
    r14=00000001f49c3860 r15=00000001f58c0040
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    # Child-SP RetAddr Call Site
    00 00000000`106fcf40 000007fe`f30c1437 sqlmin!SetidentI2I4+0x1f3
    01 00000000`106fd050 000007fe`f474e7ce sqlTsEs!CEsExec::GeneralEval4+0xe7
    02 00000000`106fd120 000007fe`f470e6ef sqlmin!CQScanUpdateNew::GetRow+0x43d
    03 00000000`106fd1d0 000007fe`f08ff517 sqlmin!CQueryScan::GetRow+0x81
    04 00000000`106fd200 000007fe`f091cebe sqllang!CXStmtQuery::ErsqExecuteQuery+0x36d
    05 00000000`106fd390 000007fe`f091ccb9 sqllang!CXStmtDML::XretDMLExecute+0x2ee
    06 00000000`106fd480 000007fe`f08fa058 sqllang!CXStmtDML::XretExecute+0xad
    07 00000000`106fd4b0 000007fe`f08fb66b sqllang!CMsqlExecContext::ExecuteStmts<1,1>+0x427
    08 00000000`106fd5f0 000007fe`f08fac2e sqllang!CMsqlExecContext::FExecute+0xa33
    09 00000000`106fd7e0 000007fe`f152cfaa sqllang!CSQLSource::Execute+0x86c
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    0b 00000000`106fda30 000007fe`f152a1d8 sqllang!CStmtExecProc::XretExecExecute+0x4e8
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    12 00000000`106ff200 000007fe`f2bf47b4 sqldk!SOS_Task::Param::Execute+0x21e
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    14 00000000`106ff870 000007fe`f2c136ff sqldk!SOS_Scheduler::ProcessTasks+0x279
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    16 00000000`106ff990 000007fe`f2c13246 sqldk!SystemThread::RunWorker+0x8f
    17 00000000`106ff9c0 000007fe`f2c13558 sqldk!SystemThreadDispatcher::ProcessWorker+0x3ab
    18 00000000`106ffa70 00000000`775d59ed sqldk!SchedulerManager::ThreadEntryPoint+0x226
    19 00000000`106ffb10 00000000`7780c541 kernel32!BaseThreadInitThunk+0xd
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    000007fe`f4d865ad 4c8b10 mov r10,qword ptr [rax]
    000007fe`f4d865b0 4489642438 mov dword ptr [rsp+38h],r12d
    000007fe`f4d865b5 4489642430 mov dword ptr [rsp+30h],r12d
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    000007fe`f4d865bf 4533c9 xor r9d,r9d
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    000007fe`f4d865c5 c644242801 mov byte ptr [rsp+28h],1
    000007fe`f4d865ca 4488642420 mov byte ptr [rsp+20h],r12b
    000007fe`f4d865cf 41ff5250 call qword ptr [r10+50h]
    000007fe`f4d865d3 488b10 mov rdx,qword ptr [rax] <=================== AV happened over here
    000007fe`f4d865d6 488bc8 mov rcx,rax
    000007fe`f4d865d9 4c8bf0 mov r14,rax
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