Updating tables without contaminating the data

Question

Hi,
We have two tables called EMP and DEPT
SQL >DESC EMP;
Name Null? Type
EMP_ID NOT NULL NUMBER(12)
EMPNAME NOT NULL VARCHAR2(25)
DEPT_NO NUMBER(10)
SQL >DESC DEPT;
Name Null? Type
DEPT_NO NOT NULL NUMBER(10)
DEPTNAME NOT NULL VARCHAR2(25)
We don't have any foreign key constraints in between these two tables.
We have already data in both these tables..
For Ex in DEPT table.
1 ACCOUNTS
2 SALES
3 FABRICATION
We would like to change this table to
2 ACCOUNTS
3 SALES
1 FABRICATION
These are sample records . We have huge amount of data.
How to solve this problem with out contaminating the data in the EMP Table..
Thanks in Advance..
-Sateesh

Answer 1

Kevin,
Right you are. Must be too early for me.
How about udpate to some other number(s) first, then the actual number
Using his example data
FIRST
update dept set dept_no = 10 where dept_no = 1 ;
update dept set dept_no = 20 where dept_no = 2;
update dept set dept_no = 30 where dept_no = 3;
THEN
update dept set dept_no = 2 where dept_no = 10;
update dept set dept_no = 3 where dept_no = 20;
update dept set dept_no = 1 where dept_no = 30;