Find values from one SQL Server database table not present in another table

Question

I have two tables with the following data (that I did not create nor can I control) that correlate on table1.workgroup = table2.id.

Table1

identity_id	workgroup
58173	158938173
98156	670451782
41930	159381738

Table2

id	name
158938173	Sales
670451782	Engineering
159381738	Support

I need to find where table1.workgroup does not have a correlating record in table2.

Answer 1

SELECT workgroup
FROM TABLE_1 
  EXCEPT
SELECT id
FROM TABLE_2

Answer 2

Yet another option:

SELECT Table1.workgroup
FROM      Table1
LEFT JOIN Table2 
       ON Table1.workgroup = Table2.id
WHERE Table2.id IS NULL