Check used characters

check_used_characters.sql

-- Based on https://stackoverflow.com/a/2926213/25182

WITH a AS (SELECT LTRIM(dut_eosonum) AS s, '' AS x, 0 AS n
           FROM dbo.[dutmast]
           WHERE LEN(dut_eosonum)>0
           UNION ALL
           SELECT a.s, SUBSTRING(a.s, n+1, 1) AS x, n+1 AS n FROM a WHERE n<LEN(a.s))
SELECT x, COUNT(*) AS c FROM a WHERE n>0 GROUP BY x ORDER BY x
OPTION(MAXRECURSION 0);