Method-1
------------
DECLARE @String varchar(32)='AAABABCDEDE'
SELECT Occuring = LEN(@String)-
LEN (REPLACE(REPLACE(REPLACE(
@String,
'A',''),
'D',''),
'E',''))
Method-2
------------
DECLARE @String VARCHAR(100) = 'AAABABCDEDE'
SELECT SUBSTRING(@String, Number, 1) AS Character,
COUNT(*) AS Items,
SUM(COUNT(*)) OVER () AS Total
FROM master..spt_values
WHERE Number BETWEEN 1 AND LEN(@String)
AND Type = 'P'
AND SUBSTRING(@String, Number, 1) IN ('A', 'D', 'E')
GROUP BY SUBSTRING(@String, Number, 1)
