Quickest query to check for the existence of a row in Oracle?

Question

I\'m using Oracle, and I have a very large table. I need to check for the existence of any row meeting some simple criteria. What\'s the best way to go about this using simple

Answer 1

Using COUNT(*) is OK if you also use rownum=1:

declare
   l_cnt integer;
begin
   select count(*)
   into   l_cnt
   from   x
   where  x.col_a = value_a 
   and    x.col_b = value_b
   and    rownum = 1;
end;

This will always return a row, so no need to handle any NO_DATA_FOUND exception. The value of l_cnt will be 0 (no rows) or 1 (at least 1 row exists).