Re: Update Question If the Data is The Same

From: Howard J. Rogers <howardjr2000_at_yahoo.com.au>
Date: Sat, 12 Oct 2002 11:47:43 +1000
Message-ID: <b3Lp9.51065$g9.148146@newsfeeds.bigpond.com>

It does the update.

Proof?

C:\Documents and Settings\Howard>sqlplus scott/tiger_at_db9

SQL*Plus: Release 9.2.0.1.0 - Production on Sat Oct 12 11:44:30 2002 Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved. Connected to:
Oracle9i Enterprise Edition Release 9.2.0.1.0 - Production With the Partitioning, OLAP and Oracle Data Mining options JServer Release 9.2.0.1.0 - Production

SQL> select * from emp;

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- -

7369 SMITH CLERK 7902 17/DEC/80 800 20

7499 ALLEN SALESMAN 7698 20/FEB/81 1600 300 30

7521 WARD SALESMAN 7698 22/FEB/81 1250 500 30

7566 JONES MANAGER 7839 02/APR/81 2975 20

7654 MARTIN SALESMAN 7698 28/SEP/81 1250 1400 30

7698 BLAKE MANAGER 7839 01/MAY/81 2850 30

7782 CLARK MANAGER 7839 09/JUN/81 2450 10

7788 SCOTT ANALYST 7566 19/APR/87 3000 20

7839 KING PRESIDENT 17/NOV/81 5000 10

7844 TURNER SALESMAN 7698 08/SEP/81 1500 0 30

7876 ADAMS CLERK 7788 23/MAY/87 1100 20

7900 JAMES CLERK 7698 03/DEC/81 950 30

7902 FORD ANALYST 7566 03/DEC/81 3000 20

7934 MILLER CLERK 7782 23/JAN/82 1300 10
14 rows selected.

SQL> set autotrace on statistics;
SQL> update emp set sal=800 where empno=7369;

1 row updated.

Statistics

          2  recursive calls
          3  db block gets
          2  consistent gets
          1  physical reads
        632  redo size
        617  bytes sent via SQL*Net to client
        535  bytes received via SQL*Net from client
          3  SQL*Net roundtrips to/from client
          2  sorts (memory)
          0  sorts (disk)
          1  rows processed

Note that this generated some redo, block gets and consistent gets. It did work on the database, even though it didn't really change anything from (y)our perspective.

Regards
HJR "Niko" <nick_wakefield_at_hotmail.com> wrote in message news:9da94cd1.0210111725.1a57c730_at_posting.google.com...
> Hi,
>
> Does anyone know that what the database does if you do an update and
> the value you are setting is the same as what you are setting it to.
>
> e.g
>
> SALES
> ID, VALUE
> 1 1000
> 2 2000
>
>
> update SALES set VALUE = 1000 where ID = 1;
>
> Does it not do the update or will it actually do the update eventhough
> the data is the same.
>
> TIA
Received on Fri Oct 11 2002 - 20:47:43 CDT