fastest way to find non-matching ids from two tables

Question

I have base table with 1000 values. and second temporary table with 100 values. I need to compare them by guids and return only those rows from second table that do not exist in first table. I need the fastest performance solution for that. Thanks!

Answer 1

The classic left join/isnull test

select A.*
from secondTbl A
left join firstTbl B on A.guid = B.guid
WHERE B.guid is null

Answer 2

SELECT * FROM Table2 WHERE 
    NOT EXISTS (SELECT 'x' FROM table1 where 
        table1.field= table2.field)

http://weblogs.sqlteam.com/mladenp/archive/2007/05/18/60210.aspx