I just want to add my support of this being a feature request. Has anyone heard if we will be able to assign %(DB.NULL) to a token in any future release of WF?

The current process I'm working on needs to insert/update a lot of data to a table but only if the field is not empty. By just updating all the columns directly from their associated field values, it creates empty columns, not NULL, if a field value is blank. Other components of the process (i.e. lookup rules in a related form, other workflows, etc.) are looking to see if a value is returned from these columns. Since empty is not the same as NULL, I either have to implement a bunch of conditionals in the original workflow that will need to be maintained or, as previously suggested, update/insert using a custom query (this is the route I will be taking) in order to insert the NULL that subsequent components rely on. In any case, being able to just modify a token with %(DB.NULL) (or something that achieves the same outcome) would sure save a lot of time.

The concept discussed here is cool but specifically doesn't accommodate inserting NULL into a database.

Only way i was able to write NULL to database was by using custom query.

UPDATE [LFRefDB].[dbo].[EmployeesTest]
SET [Middle_Name]=NULL
  WHERE [ID]=8

When i try to use Token value as parameter or use update data activity(with or without token), column is updated with 'NULL' instead of actual NULL.

The DB.NULL token is useful if you would like to clear a Laserfiche Forms variable in the middle of a process. 

If you would like to set a NULL value using one of the databse activities, you can use this token: