I have seen people having hard time when they try to achieve similar functionality which is provided by "Except" keyword in T-SQL. I am talking about the case when people need to select those records from one table which are not available in another table.
Well, if both these tables are in one database, you can definately use SQL query and make use of Except keywork. But if tables are in different database then... And then people start experimenting with Merge Join Task and later start googling it.
One of the mandatory condition while using the Merge Join Task is to provide the matching key. And we want those keys (Records) which are not matching. Simple answer to this is - Lookup Task.
Find out yourself in following screen-shot:
So, you can use this whenever you come across such requirements. I hope you will find this handy.
Khilitchandra V. Prajapati