Count Number of Particular Character of String Oracle SQl,Remove Particular character

The below Query Display Number of 'a' either it is upper case or lower case.


select first_name,length(first_name)-length(replace(lower(first_name), 'a')) from employees; 


Count The Number of 'A'
select first_name,length(first_name)-length(replace(first_name, 'A')) from employees;