How to recode a field into this specific structure using T-SQL? - sql

Question

I am using SQL Server 2014 and I have a column (ID) in a table (tbl1). The column ID is a nvarchar field.
Here are some examples of what it contains:
ID
18FD64245
533040174
12AZ61356
19AK13355
18HD24189
I would like to run a T-SQL query to recode those values based on the following logic:
IF THEN IF THEN
A 1 0 3
B 2 1 6
C 3 2 7
D 4 3 1
E 5 4 2
F 6 5 4
G 7 6 8
H 8 7 9
I 9 8 5
J 10 9 0
K 11
L 12
M 13
N 14
O 15
P 16
Q 17
R 18
S 19
T 20
U 21
V 22
W 23
X 24
Y 25
Z 26
Therefore the first 2 values shown above would be recoded as:
ID ID2
18FD64245 656482724
533040174 411323692
I am having a hard time approaching the problem from a T-SQL point of view. I am thinking about using CASE Statements to solve the problem. I also had a look at the REPLACE function.
But I am stuck as to how to go about it since the ID field is an alpha-numeric field.
Any ideas on how I move forward with this?
Edit (to show my sql codes as per answer proposed by #Squirrel):
declare #map table
(
map_fr char(1),
map_to varchar(2)
)
insert into #map
values
('A', '1'),
('B', '2'),
('C', '3'),
('D', '4'),
('E', '5'),
('F', '6'),
('G', '7'),
('H', '8'),
('I', '9'),
('J', '10'),
('K', '11'),
('L', '12'),
('M', '13'),
('N', '14'),
('O', '15'),
('P', '16'),
('Q', '17'),
('R', '18'),
('S', '19'),
('T', '20'),
('U', '21'),
('V', '22'),
('W', '23'),
('X', '24'),
('Y', '25'),
('Z', '26')
; with rcte as
(
select [ID], idx = 1, ch = substring([ID], 1, 1)
from Table1
WHERE [ID] IS NOT NULL
union all
select [ID], idx = idx + 1, ch = substring([ID], idx + 1, 1)
from rcte
where idx < len([ID])
),
cte as
(
select r.[ID], r.idx, m.map_to
from rcte r
inner join #map m on r.ch = m.map_fr
)
select [ID],
(select '' + map_to from cte x where x.[ID] = c.[ID] order by idx for xml path('')) as ID2
from cte c
group by [ID]
order by [ID]

Answer 1

I would create a mapping table like
declare #map table
(
map_fr char(1),
map_to varchar(2)
)
and insert the mapping there
insert into #map
values ('A', '1'), ('B', '2'), ('C', '3'), ('D', '4'), ('E', '5'), ('F', '6'),
('G', '7'), ('H', '8'), ('I', '9'), ('J', '10'),('K', '11'),('L', '12'),
('M', '13'),('N', '14'),('O', '15'),('P', '16'),('Q', '17'),('R', '18'),
('S', '19'),('T', '20'),('U', '21'),('V', '22'),('W', '23'),('X', '24'),
('Y', '25'),('Z', '26'),
('0', '3'), ('1', '6'), ('2', '7'), ('3', '1'), ('4', '2'), ('5', '4'),
('6', '8'), ('7', '9'), ('8', '5'), ('9', '0')
then use recursive CTE to split the character and join to the mapping table. And finally concatenate back the string using the mapped value.
; with rcte as
(
select ID, idx = 1, ch = substring(ID, 1, 1)
from yourtbl
union all
select ID, idx = idx + 1, ch = substring(ID, idx + 1, 1)
from rcte
where idx < len(ID)
),
cte as
(
select r.ID, r.idx, m.map_to
from rcte r
inner join #map m on r.ch = m.map_fr
)
select ID,
(select '' + map_to from cte x where x.ID = c.ID order by idx for xml path('')) as ID2
from cte c
group by ID
order by ID

Answer 2

This is better suited as an scalar function, but if you want to do it all on a single SQL statement, here is a way :
select ID,
case substring(ID, 1, 1) when 'A' then '1'
when 'B' then '2'
...
when '9' then '0'
end
+
case substring(ID, 2, 1) when 'A' then '1'
when 'B' then '2'
...
when '9' then '0'
end
+
...
...
case substring(ID, 9, 1) when 'A' then '1'
when 'B' then '2'
...
when '9' then '0'
end
as ID2
from MY_TABLE

Answer 3

You can also map these using a tally table and some of the new features of SQL Server 2017 (STRING_AGG):
SQL Fiddle
MS SQL Server 2017 Schema Setup:
CREATE TABLE IDS
(
ID NVARCHAR(9)
)
INSERT INTO IDS
VALUES ('18FD64245'),
('533040174'),
('12AZ61356'),
('19AK13355'),
('18HD24189');
Query 1:
WITH Tally
AS
(
SELECT ROW_NUMBER() OVER (ORDER BY Nums.Num) AS Number
FROM (VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(10)) AS Nums(Num)
CROSS APPLY (VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(10)) AS Nums2(Num)
),
Chars
As
(
-- Turn each character of ID to new row
SELECT ID, SUBSTRING(ID, Number, 1) AS OldChar, Number As Ind
FROM IDS
CROSS APPLY Tally
WHERE SUBSTRING(ID, Number, 1) <> ''
),
NewChars
AS
(
-- Map old characters to new characters
SELECT *,
CASE WHEN ISNumeric(OldChar) = 1 THEN
-- effectively a mapping string to map old characters to new
SUBSTRING('3671248950', CHARINDEX(OldChar, '0123456789'), 1)
ELSE
-- for alphanumeric we can simply make 'A' be 1 and 'B' be 2
-- by subtracting the ASCII value of 'A' from the ASCII of the
-- Character and add 1
ASCII(OldChar) - ASCII('A') + 1
END As NewChar
FROM Chars
)
-- Recombine New Characters to form new Id (SQL Server 2017 only)
SELECT ID, STRING_AGG(NewChar,'') WITHIN GROUP (ORDER BY Ind) AS NewId
FROM NewChars
GROUP BY ID
ORDER BY Id
Results:
| ID | NewId |
|-----------|------------|
| 12AZ61356 | 6712686148 |
| 18FD64245 | 656482724 |
| 18HD24189 | 658472650 |
| 19AK13355 | 6011161144 |
| 533040174 | 411323692 |