Sequencies in string
DECLARE @s VARCHAR(100)
SET @s = 'aardddvaaaarrkkkk'
-- Highest frequency of same character
SELECT TOP 1 WITH TIES
[char],
COUNT(*) AS cnt
FROM (
SELECT SUBSTRING(@s, 1 + Number, 1) [char]
FROM master..spt_values
WHERE Number < DATALENGTH(@s)
AND type = 'P'
) AS q
GROUP BY [char]
ORDER BY COUNT(*) DESC
-- Longest sequence of same character
SELECT TOP 1 WITH TIES
[char],
CASE [seq]
WHEN 0 THEN DATALENGTH(@s) - Number
ELSE [seq]
END AS [seq]
FROM (
SELECT SUBSTRING(@s, 1 + Number, 1) [char],
Number,
PATINDEX('%[^' + SUBSTRING(@s, 1 + Number, 1) + ']%', SUBSTRING(@s, 2 + Number, 8000)) AS [seq]
FROM master..spt_values
WHERE Number < DATALENGTH(@s)
AND type = 'P'
) AS q
ORDER BY 2 DESC