Jumbling the data within the table - sql

Question

I have a scenario, where i have to mask the data with data within the table
let's say I have a table student_details(ID, CODE, NAME)
1 A XYZ
2 A 123
3 A QWERTY
I want the output as
1 A QWERTY
2 A XYZ
3 A 123
I want the name to be within the name list in that table
for same id I Want different name which is in the table.
select * from emp_details order by dbms_random.value;
is giving some random names which are not in list.
Can any one help me with this?

Answer 1

Here's one option: recalculate the ID value using ROW_NUMBER analytic function which orders rows by the hash value over concatenated name, code and id columns (that's just for example; you can pick something different).
SQL> with test (id, code, name) as
2 (select 1, 'A', 'XYZ' from dual union all
3 select 2, 'A', '123' from dual union all
4 select 3, 'A', 'QUERTY' from dual
5 ),
6 inter as
7 (select row_number() over (order by ora_hash(name || code || id)) id,
8 code, name
9 from test
10 )
11 select t.id, t.code, i.name
12 from test t join inter i on t.id = i.id;
ID C NAME
---------- - ------
1 A XYZ
2 A QUERTY
3 A 123
SQL>

Answer 2

If you intend to permutate selected columns in your table and leave the rest of the table unchanged, you may use a join with a key permutation table.
Assume your data as follows:
ID CODE NAME
---------- ---- ------
1001 A XYZ
1002 B 123
1004 C QUERTY
1005 A FOO
Note, that the PK is not continuous, wich is the generall case. If you have the PK a continuous sequence starting with 1, you may even simplify the solution (as proposed in other answer).
First lets define the permutation table assigning to each PK a new key in random order.
create table PERM as
with rn as (
select
id,
row_number() over (order by id) rn,
row_number() over (order by dbms_random.value) rn_new
from student)
select a.ID, b.ID ID_NEW
from rn a
join rn b
on a.RN = b.RN_NEW;
ID ID_NEW
---------- ----------
1001 1004
1002 1001
1004 1005
1005 1002
The query defines two row_number sequences, first in the order of the PK, second in random order. The final join gets the original and new (permutated) IDs.
Now to permute a selected colums is as easy as to join your table twice with the permutation table in between and choose preserved columns from the first table, the permuted columns from the second one.
select a.ID, a.code, b.name
from student a
join PERM p on a.id = p.id
join student b on p.id_new = b.id
order by a.id;
ID CODE NAME
---------- ---- ------
1001 A QUERTY
1002 B XYZ
1004 C FOO
1005 A 123
As far as you preserv the permutation table you can reconstruct the former state, if you drop it, there is no way to get the original data.