MSSQL中唯一的字母数字键生成

Question

I have table with char(4) field which is used as key. Value for that is generated (max + 1). But not it has reached to it's max(9999). Cannot change the data type of the column since that is used it so many places.

I came up with a solution like below...

9999 -> A000...A999->B000...B999->Z999 -> ZA00->ZZZZ (zzzz will be OK for another 10 years)

Please tell me is there an easy way to generate this other than doing substring() and string manipulation ?

Current Code :

DECLARE @cle smallint
SELECT @cle = isnull(MAX(CONVERT(smallint,RTRIM(cle))),0) from smnf
INSERT INTO smnf (sup, cle, dsc, exc, dirty) VALUES (@sup, CONVERT(char(4), @cle+1), @dsc, 0, 'A')

Answer 1

SELECT i INTO #t FROM (SELECT '0' i UNION ALL SELECT '1' UNION ALL SELECT '2' UNION ALL SELECT '3' UNION ALL SELECT '4' UNION ALL SELECT '5' UNION ALL SELECT '6' UNION ALL SELECT '7' UNION ALL SELECT '8' UNION ALL SELECT '9' UNION ALL SELECT 'A' UNION ALL SELECT 'B' UNION ALL SELECT 'C' UNION ALL SELECT 'D' UNION ALL SELECT 'E' UNION ALL SELECT 'F' UNION ALL SELECT 'G' UNION ALL SELECT 'H' UNION ALL SELECT 'I' UNION ALL SELECT 'J' UNION ALL SELECT 'K' UNION ALL SELECT 'L' UNION ALL SELECT 'M' UNION ALL SELECT 'N' UNION ALL SELECT 'O' UNION ALL SELECT 'P' UNION ALL SELECT 'Q' UNION ALL SELECT 'R' UNION ALL SELECT 'S' UNION ALL SELECT 'T' UNION ALL SELECT 'U' UNION ALL SELECT 'V' UNION ALL SELECT 'W' UNION ALL SELECT 'X' UNION ALL SELECT 'Y' UNION ALL SELECT 'Z') t

CREATE TABLE id_list (id char(4) PRIMARY KEY);

INSERT id_list
SELECT c1.i+c2.i+c3.i+c4.i
FROM #t c1, #t c2, #t c3, #t c4
WHERE c1.i+c2.i+c3.i+c4.i NOT LIKE '[0-9]%[A-Z]%'  --Eliminate alphas in the first 10000 to preserve existing ids.

When you need the next id:

DECLARE @curr_id char(4) = '9ZZZ'
DECLARE @next_id char(4)

SELECT TOP 1 @next_id = [id] FROM id_list WHERE [id] > @curr_id

PRINT @next_id

A000