MSSQL - Masking data based on mapping table - sql

Question

wanted to perform data masking according to mapping as below by using MSSQL 2008R2:
Mapping Table
A = C
B = A
C = E
1 = 3
2 = 1
3 = 9
Original
ABC123
Masked
CAE319
The idea would be using replace however the second replace function will replacing previous replaced value.
select Replace(Replace(Replace(Replace(Replace(REPLACE('ABC123', 'A', 'C'), 'B', 'A'), 'C', 'E'), '1', '3'), '2', '1'), '3', '9')
Result: CAE319
P.s. value edited, because Reverse or reverse replace cannot be use in this case
any idea?

Answer 1

If you want a more table approach.
There are two code segments below which will Mask or UnMask a string. Easily converted into a UDF or even placed in a CROSS APPLY
Declare #Mask table (MapFrom varchar(10),MapTo varchar(10))
Insert into #Mask values
('A','C'),
('B','D'),
('C','E'),
('1','2'),
('2','3'),
('3','9')
Declare #Yourtable table (ID int,SomeCol varchar(max))
Insert Into #Yourtable values
(1,'ABC123')
-- To Mask
Declare #U varchar(max) ='ABC123'
Select NewSting = Stuff((Select ''+S
From (
Select N
,S=IsNull(MapTo,Substring(#U,N,1))
From (Select Top (Len(#U)) N=Row_Number() Over (Order By (Select null)) From master..spt_values) N
Left Join #Mask on Substring(#U,N,1)=MapFrom
) X
Order By N
For XML Path ('')),1,0,'')
-- To UnMask
Declare #M varchar(max) = 'CDE239'
Select NewSting = Stuff((Select ''+S
From (
Select N
,S=IsNull(MapFrom,Substring(#M,N,1))
From (Select Top (Len(#M)) N=Row_Number() Over (Order By (Select null)) From master..spt_values) N
Left Join #Mask on Substring(#M,N,1)=MapTo
) X
Order By N
For XML Path ('')),1,0,'')

Answer 2

Just change the order of replace and reverse the result
select REVERSE( Replace(Replace(Replace(Replace(Replace(REPLACE('321CBA', '3', '9'), '2', '3'), '1', '2'), 'C', 'E'), 'B', 'D'), 'A', 'C'))
RESULT :
CDE239
EDIT:
Declare #Mask table (MapFrom varchar(10),MapTo varchar(10))
Insert into #Mask values
('A','C'),
('B','A'),
('C','E'),
('1','3'),
('2','1'),
('3','9')
DECLARE #pos INT
,#result VARCHAR(100)
,#maskfrom NCHAR(1)
,#mask_to NCHAR(1);
SET #result = 'ABC123';
SET #pos = 1
WHILE #pos < LEN(#result) + 1
BEGIN
SELECT #mask_to = MapTo
FROM #mask
WHERE MapFrom = substring(#result, #pos, 1)
SET #result = STUFF(#result, #pos, 1, #mask_to);
SET #pos = #pos + 1;
END
SELECT #result
RESULT
CAE319