fastest way to find non-matching ids from two tables

问题

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!

回答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

回答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

来源：https://stackoverflow.com/questions/6528700/fastest-way-to-find-non-matching-ids-from-two-tables