an efficient way to test if a table row exists

Question

I\'m trying to find the most efficient way to determine if a table row exists.

I have in mind 3 options:

1. SELECT EXISTS(SELECT 1 FROM table1 WHERE so

Answer 1

The exists function is defined generally in SQL, it isn't only as a MySQL function : http://www.techonthenet.com/sql/exists.php and I usually use this function to test if a particular row exists.

However in Oracle I've seen many times the other approach suggested before:

SELECT COUNT(1) FROM table 1 WHERE some_condition.