>>In your tests performance of the LEFT JOIN seems to be much worse than others. What are tables metrics and how many records did you get as a result of a query? Also, did you discharge the results or not?
>
>Yes as I told you before it was the slowest. Metric is simple. 2 million records table created, and copied onto another (structure was as simple as it can be, an ID plus a varchar data field. With a more complex structure it is likely it would be much slower). Then a few more records are added to one of them. Index created on join field.
>Cetin

Yes, it's confirmed now by this blog by Gail Show

http://sqlinthewild.co.za/index.php/2010/03/23/left-outer-join-vs-not-exists/

In conclusion - use NOT EXISTS for checking if records don't exist in another table.