Possible tuse of EXISTS in PL/SQL?

I think that somewhere I have seen EXISTS been used in a smart way to find out whether some value exists in a table. To better explain what I mean, I will show how it is I want to use it:

I have a very large table called rtest. If rtest have one or more rows with the value 'XX' in colum rcol, then I do not want to insert a new row, otherwise I will. My PL/SQL code now looks something like:

select count(*)
into rvariable
from rtest
where rcol='XX';

if rvariable=0 then
  < code to do an insert >
end if;

This select will make Oracle perform a full table scan (unless I have an index on it, which in this case I do not), but if it is possible to use EXISTS in some way, I think Oracle would stop reading the table when the first record matching the query was found(??).

Very thankful for help on this.

Kind regards,
Randi Wølner Received on Tue Oct 17 2000 - 07:27:49 CDT