Best way to test if a row exists in a MySQL table

Question

I\'m trying to find out if a row exists in a table. Using MySQL, is it better to do a query like this:

SELECT COUNT(*) AS total FROM table1 WHERE ...
         


        

Answer 1

I'd go with COUNT(1). It is faster than COUNT(*) because COUNT(*) tests to see if at least one column in that row is != NULL. You don't need that, especially because you already have a condition in place (the WHERE clause). COUNT(1) instead tests the validity of 1, which is always valid and takes a lot less time to test.