If you want to find out 'How many number of times a character/word/special symbol repeated in a string', we can use below query,
SELECT (LEN(FirstName)- LEN(REPLACE(FirstName,'s','')) FROM EmployeeTable
-- gives the length/number of characters of a string/Column ( i.e. FirstName) LEN(REPLACE(FirstName,'s',''))
-- firstly it replaces the character 'S' with empty string and then gives the length of string without character 'S'
(Total Length) - (String Length with out 'S') gives the number of occurances of a character in s string