What's the most efficient way to check if a record exists in Oracle?

Question

A)

select decode(count(*), 0, \'N\', \'Y\') rec_exists
from (select \'X\'
      from dual
      where exists (select \'X\'
                    from sales
           


        

Answer 1

select decode(count(*), 0, 'N', 'Y') rec_exists 
      from sales 
      where sales_type = 'Accessories';