Converting CHAR string to nth letter in Alphabet string in SQL - sql

Question

I have to build a process that takes a VARCHAR string (for example 'AHT559') and converts it to a INT only string by converting the Alphabetic chars to INTEGERS based on the nth letter in the alphabet. The above would thus result in: 010820559.
I have done this in SAS before, but I'm relatively new to SQL. What would be the best way to do this in SQL?
Here is what I've done in SAS:
DO _i = 1 TO length( account );
IF (rank( char( account, _i ) ) -64) < 0 THEN agreement_hash = CATS( agreement_hash, char( account, _i ) );
ELSE IF (rank( char( account, _i ) ) -64) < 10 THEN agreement_hash = CATS( agreement_hash, 0, rank( char( account, _i ) )-64 );
ELSE agreement_hash = CATS( agreement_hash, rank( char( account, _i ) )-64 );
END;

Answer 1

If the format of the values is always the same as you state in the comments and you only need to process a single value at a time you can do some simple string manipulation to convert the characters to integers using their ASCII values, and subtracting 64 to get the number of the alphabetic character:
SELECT ASCII('A') -- produces 65
SELECT ASCII('A') - 64 -- produces 1
This is a little long winded and could be done in less lines of code, but it's separated for clarity.
DECLARE #val NVARCHAR(10) = 'AHT559'
-- get first, second and third character numeric values
DECLARE #first INT = ASCII(SUBSTRING(#val, 1, 1)) - 64
DECLARE #second INT = ASCII(SUBSTRING(#val, 2, 1)) - 64
DECLARE #third INT = ASCII(SUBSTRING(#val, 3, 1)) - 64
-- join them together adding a '0' if < 10
SELECT RIGHT('0' + CAST(#first AS VARCHAR(2)), 2)
+ RIGHT('0' + CAST(#second AS VARCHAR(2)), 2)
+ RIGHT('0' + CAST(#third AS VARCHAR(2)), 2)
+ RIGHT(#val, 3)
Tested on 4 million rows:
-- temp table creation - takes approx 100 seconds on my machine
CREATE TABLE #temp (val NVARCHAR(6))
DECLARE #rowno INT = 1
SELECT #rowno = 1
WHILE #rowno <= 4000000
BEGIN
INSERT INTO #temp ( val ) VALUES ( 'AHT559' )
SELECT #rowno = #rowno + 1
END
To run this code against the entire temp table takes < 20 seconds on my machine:
SELECT val AS OrignalValue,
RIGHT('0' + CAST( ASCII(SUBSTRING(val, 1, 1)) - 64 AS VARCHAR(2)), 2)
+ RIGHT('0' + CAST( ASCII(SUBSTRING(val, 2, 1)) - 64 AS VARCHAR(2)), 2)
+ RIGHT('0' + CAST( ASCII(SUBSTRING(val, 3, 1)) - 64 AS VARCHAR(2)), 2)
+ RIGHT(val, 3) AS FormattedValue
FROM #temp

Answer 2

Here is a similar script for sqlserver, any character which is not a capital letter is assumed a digit in this syntax:
DECLARE #x varchar(100) = 'AHT559'
DECLARE #p int = len(#x)
WHILE #p > 0
SELECT #x =
CASE WHEN substring(#x, #p, 1) between 'A' and 'Z'
THEN stuff(#x, #p, 1, right(ascii(substring(#x, #p, 1)) - 64 + 100, 2))
ELSE #x END,
#p -= 1
SELECT #x
Result:
010820559

Answer 3

You could use something like the below, possibly as a scalar function to do this conversion.
DECLARE #i INT
DECLARE #Item NVARCHAR(4000) = 'AHT1234'
DECLARE #ItemTable TABLE
(
Item NCHAR(1)
)
SET #i = 1
--Split the input string into separate characters, store in temp table
WHILE (#i <= LEN(#Item))
BEGIN
INSERT INTO #ItemTable(Item)
VALUES(SUBSTRING(#Item, #i, 1))
SET #i = #i + 1
END
DECLARE #AlphaTable TABLE (
Letter NCHAR(1),
Position NVARCHAR(2)
)
-- Populate this with the whole alphabet obviously. Could be a permanent rather than temp table.
INSERT INTO #AlphaTable
( Letter, Position )
VALUES ( N'A', '01'),
(N'H', '08'),
(N'T', '20')
DECLARE #Output NVARCHAR(50)
-- Convert the output and concatenate it back to a single output.
SELECT #Output = COALESCE(#output, '') + Converted
FROM (
SELECT CASE WHEN ISNUMERIC(Item) = 1
THEN CONVERT(NVARCHAR(1), Item)
ELSE (SELECT Position FROM #AlphaTable WHERE Letter = CONVERT(NCHAR(1), Item))
END AS Converted
FROM #ItemTable
) AS T1
SELECT #Output
GO

Answer 4

Try this.
DECLARE #STR VARCHAR(MAX)= 'AHT559',
#SP INT,
#SP_STR VARCHAR(50),
#OUTPUT VARCHAR(MAX)=''
DECLARE #TEMP_STR VARCHAR(50)
SET #TEMP_STR = #STR
WHILE Patindex('%[A-Z]%', #TEMP_STR) <> 0
BEGIN
SELECT #SP = Patindex('%[A-Z]%', #TEMP_STR)
SELECT #SP_STR = Upper(LEFT(#TEMP_STR, #SP))
SELECT #SP_STR = ( Ascii(#SP_STR) - 65 ) + 1
SELECT #TEMP_STR = Stuff(#TEMP_STR, 1, #SP, '')
SET #OUTPUT += RIGHT('0' + #SP_STR, 2)
END
SELECT #OUTPUT + Substring(#STR, Patindex('%[0-9]%', #STR), Len(#STR))

Answer 5

How about using a CTE to create every combination of the first 3 letters and using that to match to:
SQL Fiddle
MS SQL Server 2008 Schema Setup:
CREATE TABLE Accounts
(
Account VARCHAR(6)
)
INSERT INTO Accounts
VALUES ('AHT559'), ('BXC556'),
('CST345')
Query 1:
;WITH AlphaToNum
AS
(
SELECT *
FROM (VALUES
('A', '01'), ('B', '02'), ('C', '03'), ('D', '04'),
('E', '05'), ('F', '06'), ('G', '07'), ('H', '08'),
('I', '09'), ('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')
) X(alpha, num)
),
MappingTable
As
(
SELECT A1.alpha + A2.alpha + A3.alpha as match, A1.num + A2.num + A3.num as val
FROM AlphaToNum A1
CROSS APPLY AlphaToNum A2
CROSS APPLY AlphaToNum A3
)
SELECT A.Account, M.val + SUBSTRING(A.Account,4, 3) As ConvertedAccount
FROM MappingTable M
INNER JOIN Accounts A
ON LEFT(A.Account,3) = M.match
Results:
| Account | ConvertedAccount |
|---------|------------------|
| AHT559 | 010820559 |
| BXC556 | 022403556 |
| CST345 | 031920345 |

Answer 6

This is probably best done using a CLR UDF, but a full answer is too long for this format.
Basically you need to create a UDF (User defined function) that takes a string (nvarchar...) as an input and returns a string as an output. You can do that with C# quite easily, and you need to wrap it with the CLR integration requirements.
You can see here for relevant information.
The code could look something like:
[Microsoft.SqlServer.Server.SqlFunction(
IsDeterministic=true,
IsPrecise=true,
SystemDataAccess=SystemDataAccessKind.None)]
public static SqlString ToNthAlpha(SqlString value)
{
if(value.IsNull)
return value;
char []chars = value.Value.ToCharArray();
StringBuilder res = new StringBuilder();
for(int i = 0; i < chars.Length; i++)
{
if(chars[i] >= 'A' && chars[i] <= 'Z')
res.AppendFormat("{0:00}", chars[i] - 'A');
res.Append(chars[i]);
}
return new SqlString(res.ToString());
}