>Hello!
>I was just wondering if i can write a query that selects all the data not found in another table. like
>select *
>from table
>where 100 is in one table... but not in the other table
>?

Try this syntax

SELECT T1.* from myTable T1 LEFT JOIN myOtherTable T2 on T1.ID = T2.ID where T2.ID IS NULL

This syntax is more robust than the other (in case you have NULLs in T2.ID) it would not select anything if using NOT IN syntax.

In addition, it's more likely to be more performant.

See also this link

http://blogs.lessthandot.com/index.php/DataMgmt/DataDesign/the-ten-most-asked-sql-server-questions--1#4