The following is an example for retrieving the sorted data with an SQL Query.
SELECT
DATA
FROM
(
SELECT '11A' AS DATA
UNION ALL
SELECT '12B'
UNION ALL
SELECT '13'
UNION ALL
SELECT '6'
UNION ALL
SELECT '6A'
) AS TestTable
ORDER BY
LEN((
CASE WHEN ISNUMERIC(DATA) = 1
THEN LEFT(DATA + '0000', LEN(DATA) + 1)
ELSE DATA
END
)),
(
CASE WHEN ISNUMERIC(DATA) = 1
THEN LEFT(DATA + '0000', LEN(DATA) + 1)
ELSE DATA
END
)