Check count and then do some work

Question

Hi,
I have a table with 10 million records. I want to check whether a value of a specific column is present or not. If the count is greather than 0, then I want to do some task and if it is 0, then I want to do some other task.
Could you please tell me what is the best way to do?
What I am doing now is: I am checking the count using count(*) and then checking the value whether that is greater than 0 or =0 and then based on the value I am doing different task.
But count(*) is slow for this big table.
So, please let me know the best possible way to do this.

Answer 1

declare
  value_exists number;
begin
  select count(*)
  into   value_exists
  from   my_table
  where  my_column = 'ABC' and
         rownum = 1;
  if value_exists = 1 then
  elsif value_exists = 0 then
  else raise_application_error(-20001,'Bad value for value_exists of '||coalesce(to_char(value_exists),'NULL'));
  end if;
end;