Sharepoint Workflow: Check if a field is empty [Sharepoint 2010]

The Sharepoint workflows are powerful but sometimes stupid…

If you want to:

• Check if a Date Field is empty, then you can use a String Workflow Variable that contains your Date Field as a Short Date (SP2013) (or a String for SP2010), and then compare it to « 1/1/0001 » (or « 1/1/0001 12:00:00 AM » for SP2010)
• Check if a Currency field is empty… you cannot because it returns 0 when empty, so you have to change it to a Number field…
• Check if a Lookup field is empty, then set the Lookup field to a String variable and check if this variable is empty